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Artykuły w czasopismach na temat „Neutral clusters”

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Autor: Grafiati

Data publikacji: 4 czerwca 2021

Data aktualizacji: 20 lutego 2023

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1

Tuyet, Nguyen Thi Ngoc. "NEUTRAL AND CATIONIC TITANIUM-DOPED SILICON CLUSTERS: GROWTH MECHANISM AND STABILIT". Vietnam Journal of Science and Technology 55, nr 6A (23.04.2018): 83. http://dx.doi.org/10.15625/2525-2518/55/6a/12368.

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We report ab-initio study on neutral and cationic titanium-doped silicon clusters TiSin0/+ (n = 1-10). The growth patterns for both neutral and charged clusters are revealed. The neutral TiSin clusters follow a consistent rule of addition: the larger TiSin cluster is built up by adding a Si atom on the smaller TiSin-1 cluster. However, the Ti atom prefers to substitute at a high-coordination position to form the cationic clusters. The neutral TiSin clusters is more stable than the pure Sin+1 clusters while the cationic TiSin+ is less stable than the pure ones. Both neutral and cationic clusters tend to loss Si atom rather than Ti atoms.

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2

Ortega, I. K., T. Olenius, O. Kupiainen-Määttä, V. Loukonen, T. Kurtén i H. Vehkamäki. "Electrical charging changes the composition of sulfuric acid–ammonia/dimethylamine clusters". Atmospheric Chemistry and Physics 14, nr 15 (12.08.2014): 7995–8007. http://dx.doi.org/10.5194/acp-14-7995-2014.

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Abstract. Sulfuric acid clusters stabilized by base molecules are likely to have a significant role in atmospheric new-particle formation. Recent advances in mass spectrometry techniques have permitted the detection of electrically charged clusters. However, direct measurement of electrically neutral clusters is not possible. Mass spectrometry instruments can be combined with a charger, but the possible effect of charging on the composition of neutral clusters must be addressed in order to interpret and understand the measured data. In the present work we have used formation free energies from quantum chemical methods to calculate the evaporation rates of electrically charged (both positive and negative) sulfuric acid–ammonia/dimethylamine clusters. To understand how charging will affect the composition of electrically neutral clusters, we have compared the evaporation rates of the most stable neutral clusters with those of the corresponding charged clusters. Based on the evaporation rates of different molecules from the charged clusters, we determined the most likely resulting cluster composition when a stable neutral cluster is charged and the molecules with the highest evaporation rates are lost from it. We found that all of the most stable neutral clusters will be altered by both positive and negative charging. In the case of charging clusters negatively, base molecules will completely evaporate from clusters with 1 to 3 sulfuric acid molecules in the case of ammonia, and from clusters with 1 or 2 sulfuric acid molecules in the case of dimethylamine. Larger clusters will maintain some base molecules, but the H2SO4 : base ratio will increase. In the case of positive charging, some of the acid molecules will evaporate, decreasing the H2SO4 : base ratio.

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3

Suvitha, Ambigapathy, i Natarajan Sathiyamoorthy Venkataramanan. "DFT calculations on polarizabilities and hyperpolarizabilities for the neutral and anionic yttrium oxide clusters". Journal of Theoretical and Computational Chemistry 14, nr 07 (listopad 2015): 1550049. http://dx.doi.org/10.1142/s0219633615500492.

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The electronic properties, polarizabilities, first and second hyperpolarizabilities of YOn clusters of [Formula: see text]–12 were studied using the quantum chemical method. The vertical ionization potential (VIP) values for the anionic clusters increase monotonically with the cluster size. Among the neutral clusters YO3 and YO8 have the least chemical hardness values, where in anionic clusters with size [Formula: see text] possesses the least chemical hardness. Anionic clusters have more electrons attracting tendency than the neutral clusters. The computed static mean polarizability of neutral yttrium oxides has positive values but is close to zero. The incorporation of oxygen atom quenches the polarizability of yttrium. The computed polarizability anisotropy of neutral clusters shows an oscillatory effect both at static and at dynamic conditions. The first hyperpolarizability for many YOn clusters are close to zero. The existence of high symmetry in these clusters reduces the first hyperpolarizability values which was supported by the small dipole moments. The computed [Formula: see text] values for the static neutral and anionic clusters show only a small variation. The decrease in the polarizability and second hyperpolarizability with size can be interpreted in terms of the electronic delocalization and chemical bonding in the clusters.

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4

Kupiainen, O., I. K. Ortega, T. Kurtén i H. Vehkamäki. "Amine substitution into sulfuric acid – ammonia clusters". Atmospheric Chemistry and Physics Discussions 11, nr 11 (18.11.2011): 30853–75. http://dx.doi.org/10.5194/acpd-11-30853-2011.

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Abstract. The substitution of ammonia by dimethylamine in sulfuric acid – ammonia – dimethylamine clusters was studied using a collision and evaporation dynamics model. Quantum chemical formation free energies were computed using B3LYP/CBSB7 for geometries and frequencies and RI-CC2/aug-cc-pV(T+d)Z for electronic energies. We first demonstrate the good performance of our method by a comparison with an experimental study investigating base substitution in positively charged clusters, and then continue by simulating base exchange in neutral clusters, which cannot be measured directly. Collisions of a dimethylamine molecule with an ammonia containing positively charged cluster result in the instantaneous evaporation of an ammonia molecule, while the dimethylamine molecule remains in the cluster. According to our simulations, a similar base exchange can take place in neutral clusters, although the overall process is more complicated. Neutral sulfuric acid – ammonia clusters are significantly less stable than their positively charged counterparts, resulting in a competition between cluster evaporation and base exchange.

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5

Kupiainen, O., I. K. Ortega, T. Kurtén i H. Vehkamäki. "Amine substitution into sulfuric acid – ammonia clusters". Atmospheric Chemistry and Physics 12, nr 8 (16.04.2012): 3591–99. http://dx.doi.org/10.5194/acp-12-3591-2012.

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Abstract. The substitution of ammonia by dimethylamine in sulfuric acid – ammonia – dimethylamine clusters was studied using a collision and evaporation dynamics model. Quantum chemical formation free energies were computed using B3LYP/CBSB7 for geometries and frequencies and RI-CC2/aug-cc-pV(T+d)Z for electronic energies. We first demonstrate the good performance of our method by a comparison with an experimental study investigating base substitution in positively charged clusters, and then continue by simulating base exchange in neutral clusters, which cannot be measured directly. Collisions of a dimethylamine molecule with an ammonia containing positively charged cluster result in the instantaneous evaporation of an ammonia molecule, while the dimethylamine molecule remains in the cluster. According to our simulations, a similar base exchange can take place in neutral clusters, although the overall process is more complicated. Neutral sulfuric acid – ammonia clusters are significantly less stable than their positively charged counterparts, resulting in a competition between cluster evaporation and base exchange.

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6

Bréchignac, C., Ph Cahuzac i J. Ph Roux. "Photoionization of potassium clusters: Neutral and ionic cluster stabilities". Journal of Chemical Physics 87, nr 1 (lipiec 1987): 229–38. http://dx.doi.org/10.1063/1.453621.

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7

Kontkanen, J., E. Järvinen, H. E. Manninen, K. Lehtipalo, J. Kangasluoma, S. Decesari, G. P. Gobbi, A. Laaksonen, T. Petäjä i M. Kulmala. "High concentrations of sub-3 nm clusters and frequent new particle formation observed in the Po Valley, Italy, during the PEGASOS 2012 campaign". Atmospheric Chemistry and Physics Discussions 15, nr 22 (24.11.2015): 33077–119. http://dx.doi.org/10.5194/acpd-15-33077-2015.

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Abstract. The concentrations of neutral and charged sub-3 nm clusters and their connection to new particle formation (NPF) were investigated during the PEGASOS campaign (7 June–9 July 2012) at the San Pietro Capofiume measurement station in the Po Valley, Italy. Continuous high concentrations of sub-3 nm clusters were detected during the measurement period, although the condensation sink was relatively high (median value 1.1 × 10-2 s-1). The median cluster concentrations were 2140 and 7980 cm-3 in the size bins of 1.5–1.8 nm and 1.8–3 nm, and the majority of them were electrically neutral. NPF events were observed during the measurement period frequently, on 86 % of the days. The median growth rates of clusters during the events were 4.3, 6.0 and 7.2 nm h-1 in the size ranges of 1.5–3, 3–7 and 7–20 nm. The median formation rate of 1.6 nm clusters was high, 45 cm-3 s-1, and it exceeded the median formation rate of 2 nm clusters by one order of magnitude. The ion-induced nucleation fraction was low; the median values were 0.7 % at 1.6 nm and 3.0 % at 2 nm. On NPF event days the neutral cluster concentration had a maximum around 9 a.m. (local winter time), which was absent on a non-event day. The increase in the cluster concentrations in the morning coincided with the increase in the boundary layer height. At the same time radiation and temperature increased and RH and condensation sink decreased. The concentration of neutral clusters was observed to have apositive correlation with sulfuric acid proxy, indicating the significance of sulfuric acid for the cluster formation in San Pietro Capofiume. The condensation sink had anegative correlation with the concentration of charged clusters but no clear relation to the neutral cluster concentration. This finding, together with back-trajectory analysis, suggests that the precursor vapors of the clusters and background aerosol particles, acting as their sink, have possibly originated from the same sources, including e.g. power plants and industrial areas in the Po Valley.

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8

Lehtipalo, K., M. Sipilä, I. Riipinen, T. Nieminen i M. Kulmala. "Analysis of atmospheric neutral and charged molecular clusters in boreal forest using pulse-height CPC". Atmospheric Chemistry and Physics 9, nr 12 (23.06.2009): 4177–84. http://dx.doi.org/10.5194/acp-9-4177-2009.

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Abstract. We measured the size distribution of atmospheric neutral and charged clusters and particles down to mobility diameter around 1.5 nm by applying pulse-height CPC technique at SMEAR II station in Hyytiälä, southern Finland during spring 2007 and May 2008. The concentration of molecular clusters smaller than 3 nm seems to be highly variable in boreal forest environment, the concentration varied typically between 500–50 000 cm−3. By comparing to concentrations measured with ion spectrometers, we conclude that ion clusters and neutral clusters produced by ion-ion recombination are usually not sufficient to explain all of the observed clusters; the median fraction of recombination products from all neutral clusters was 4.9%. Before and during most new particle formation events the cluster formation rate rose only slightly, or remained close to stable. Nocturnal formation of clusters was also frequently observed.

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9

Jokinen, T., M. Sipilä, H. Junninen, M. Ehn, G. Lönn, J. Hakala, T. Petäjä, R. L. Mauldin III, M. Kulmala i D. R. Worsnop. "Atmospheric sulphuric acid and neutral cluster measurements using CI-APi-TOF". Atmospheric Chemistry and Physics Discussions 11, nr 12 (6.12.2011): 31983–2002. http://dx.doi.org/10.5194/acpd-11-31983-2011.

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Abstract. The first ambient measurements using nitrate ion based Chemical Ionization with the Atmospheric Pressure interface Time-Of-Flight mass spectrometer (CI-APi-TOF) for sulphuric acid and neutral cluster detection are presented. We have found CI-APi-TOF a highly stable and sensitive tool for molecular sulphuric acid detection. The lowest limit of detection for sulphuric acid was determined to be 3 × 104 molecules cm−3 for two hour averaging. Signals from sulphuric acid clusters up to tetramer accompanied by ammonia were also obtained but these were found to result from naturally charged clusters formed by ion induced clustering in the atmosphere during nucleation. Opposite to earlier studies with cluster mass spectrometers, we had no indication of neutral clusters. The reason is either less efficient charging of clusters in comparison to molecular sulphuric acid, or in low concentration of neutral clusters at our measurement site during these particular nucleation events. We show that utilizing high resolution mass spectrometry is crucial in separating the weak sulfuric acid cluster signal from the other compounds.

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10

Jokinen, T., M. Sipilä, H. Junninen, M. Ehn, G. Lönn, J. Hakala, T. Petäjä, R. L. Mauldin, M. Kulmala i D. R. Worsnop. "Atmospheric sulphuric acid and neutral cluster measurements using CI-APi-TOF". Atmospheric Chemistry and Physics 12, nr 9 (9.05.2012): 4117–25. http://dx.doi.org/10.5194/acp-12-4117-2012.

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Abstract. The first ambient measurements using nitrate ion based Chemical Ionization with the Atmospheric Pressure interface Time-Of-Flight mass spectrometer (CI-APi-TOF) for sulphuric acid and neutral cluster detection are presented. We have found CI-APi-TOF a highly stable and sensitive tool for molecular sulphuric acid detection. The lowest limit of detection for sulphuric acid was determined to be 3.6 × 104 molecules cm−3 for 15 min averaging. Signals from sulphuric acid clusters up to tetramer containing ammonia were also obtained but these were found to result from naturally charged clusters formed by ion induced clustering in the atmosphere during nucleation. Opposite to earlier studies with cluster mass spectrometers, we had no indication of neutral clusters. The reason is either less efficient charging of clusters in comparison to molecular sulphuric acid, or the low concentration of neutral clusters at our measurement site during these particular nucleation events. We show that utilizing high resolution mass spectrometry is crucial in separating the weak sulfuric acid cluster signal from other compounds.

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11

Hofer, Wolfgang O., i Hubert Gnaser. "Anisotropic emission of neutral clusters". Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 18, nr 1-6 (styczeń 1986): 605–8. http://dx.doi.org/10.1016/s0168-583x(86)80096-9.

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12

Treml, T. F. "Asymptotic behaviour of nonlocal effective potentials in two-cluster atomic scattering". Canadian Journal of Physics 63, nr 10 (1.10.1985): 1353–56. http://dx.doi.org/10.1139/p85-224.

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Dilation and boost transformations are used to study the nonlocal effective potentials in two-cluster atomic scattering below the lowest three-cluster threshold, where the particles interact via two-body Coulomb potentials and at least one cluster is neutral. Boost analyticity is used to express the rotated potential in a form that displays explicitly its behaviour for large values of the cluster separation. When one cluster is neutral, the nonlocal effective potential falls off, in some sense, as r−4 for large values of r, where r is the distance between the centres of mass of the two clusters. When both clusters are neutral, the nonlocal potential can be shown to fall off as r−5 for large values of r.

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13

Yamada, Akira, Ken Miyajima i Fumitaka Mafuné. "Catalytic reactions on neutral Rh oxide clusters more efficient than on neutral Rh clusters". Physical Chemistry Chemical Physics 14, nr 12 (2012): 4188. http://dx.doi.org/10.1039/c2cp24036j.

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14

Lehtipalo, K., M. Sipilä, I. Riipinen, T. Nieminen i M. Kulmala. "Analysis of atmospheric neutral and charged molecular clusters in boreal forest using pulse-height CPC". Atmospheric Chemistry and Physics Discussions 8, nr 6 (10.12.2008): 20661–85. http://dx.doi.org/10.5194/acpd-8-20661-2008.

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Abstract. We measured the size distribution of atmospheric neutral and charged clusters and particles down to mobility diameter around 1.5 nm by applying pulse-height CPC technique at SMEAR II station in Hyytiälä, southern Finland during spring 2007 and May 2008. The concentration of molecular clusters smaller than 3 nm seems to be highly variable in boreal forest environment. The concentration varied typically between 500–50 000 cm−3, the medians being 8060 cm−3 in year 2007 and 3380 cm−3 in 2008. By comparing to concentrations measured with ion spectrometers, we conclude that ion clusters and neutral clusters produced by ion-ion recombination are usually not sufficient to explain all of the observed clusters; the median fraction of recombination products from all neutral clusters was 4.9%. Before and during most new particle formation events the cluster formation rate rose only slightly, or remained close to stable. Nocturnal formation of clusters was also frequently observed.

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15

Kontkanen, Jenni, Emma Järvinen, Hanna E. Manninen, Katrianne Lehtipalo, Juha Kangasluoma, Stefano Decesari, Gian Paolo Gobbi, Ari Laaksonen, Tuukka Petäjä i Markku Kulmala. "High concentrations of sub-3nm clusters and frequent new particle formation observed in the Po Valley, Italy, during the PEGASOS 2012 campaign". Atmospheric Chemistry and Physics 16, nr 4 (19.02.2016): 1919–35. http://dx.doi.org/10.5194/acp-16-1919-2016.

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Abstract. The concentrations of neutral and charged sub-3nm clusters and their connection to new particle formation (NPF) were investigated during the PEGASOS campaign (7 June–9 July 2012) at the San Pietro Capofiume measurement station in the Po Valley, Italy. Continuous high concentrations of sub-3nm clusters were detected during the measurement period, although the condensation sink was relatively high (median value 1.1 × 10−2 s−1). The median cluster concentrations were 2140 and 7980 cm−3 in the size bins of 1.5–1.8 and 1.8–3 nm, and the majority of them were electrically neutral. NPF events were observed during the measurement period frequently, on 86 % of the days. The median growth rates of clusters during the events were 4.3, 6.0 and 7.2 nm h−1 in the size ranges of 1.5–3, 3–7 and 7–20 nm. The median formation rate of 1.6 nm clusters was high, 45 cm−3 s−1, and it exceeded the median formation rate of 2 nm clusters by 1 order of magnitude. The ion-induced nucleation fraction was low; the median values were 0.7 % at 1.6 nm and 3.0 % at 2 nm. On NPF event days the neutral cluster concentration had a maximum around 09:00 (local winter time), which was absent on a non-event day. The increase in the cluster concentrations in the morning coincided with the increase in the boundary layer height. At the same time radiation, temperature and SO2 concentration increased, and RH and condensation sink decreased. The concentrations of neutral and charged clusters were observed to have a positive correlation with sulfuric acid proxy, indicating the significance of sulfuric acid for the cluster formation in San Pietro Capofiume. The condensation sink had a negative correlation with the concentration of charged clusters but no clear relation to the neutral cluster concentration. This finding, together with back-trajectory analysis, suggests that the precursor vapors of the clusters and background aerosol particles, acting as their sink, have possibly originated from the same sources, including e.g., power plants and industrial areas in the Po Valley.

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16

Ortega, I. K., T. Olenius, O. Kupiainen-Määttä, V. Loukonen, T. Kurtén i H. Vehkamäki. "Electrical charging changes the composition of sulfuric acid-ammonia/dimethylamine clusters". Atmospheric Chemistry and Physics Discussions 14, nr 2 (16.01.2014): 1317–48. http://dx.doi.org/10.5194/acpd-14-1317-2014.

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Abstract. Sulfuric acid clusters stabilized by base molecules are likely to have a significant role in atmospheric new particle formation. Recent advances in mass spectrometry techniques have permitted the detection of electrically charged clusters. However, direct measurement of electrically neutral clusters is not possible. Mass spectrometry instruments can be combined with a charger, but the possible effect of charging on the composition of neutral clusters must be addressed before the measured data can be linked to properties of neutral clusters. In the present work we have used formation free energies from quantum chemical methods to calculate the evaporation rates of electrically charged (both positive and negative) sulfuric acid-ammonia/dimethylamine clusters. To understand how charging will affect the composition of these clusters, we have compared the evaporation rates of charged clusters with those of the corresponding neutral clusters. We found that the only cluster studied in this paper which will retain its composition is H2SO4 · NH3 when charged positively; all other clusters will be altered by both positive and negative charging. In the case of charging clusters negatively, base molecules will completely evaporate from clusters with 1 to 3 sulfuric acid molecules in the case of ammonia, and from clusters with 1 or 2 sulfuric acid molecules in the case of dimethylamine. Larger clusters will maintain some base molecules, but the H2SO4 : base ratio will increase. In the case of positive charging, some of the acid molecules will evaporate, decreasing the H2SO4 : base ratio.

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17

Zhao, J., J. N. Smith, F. L. Eisele, M. Chen, C. Kuang i P. H. McMurry. "Observation of neutral sulfuric acid-amine containing clusters in laboratory and ambient measurements". Atmospheric Chemistry and Physics 11, nr 21 (2.11.2011): 10823–36. http://dx.doi.org/10.5194/acp-11-10823-2011.

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Abstract. Recent ab initio calculations showed that amines can enhance atmospheric sulfuric acid-water nucleation more effectively than ammonia, and this prediction has been substantiated in laboratory measurements. Laboratory studies have also shown that amines can effectively displace ammonia in several types of ammonium clusters. However, the roles of amines in cluster formation and growth at a microscopic molecular scale (from molecular sizes up to 2 nm) have not yet been well understood. Processes that must be understood include the incorporation of amines into sulfuric acid clusters and the formation of organic salts in freshly nucleated particles, which contributes significantly to particle growth rates. We report the first laboratory and ambient measurements of neutral sulfuric acid-amine clusters using the Cluster CIMS, a recently-developed mass spectrometer designed for measuring neutral clusters formed in the atmosphere during nucleation. An experimental technique, which we refer to as Semi-Ambient Signal Amplification (SASA), was employed. Sulfuric acid was added to ambient air, and the concentrations and composition of clusters in this mixture were analyzed by the Cluster CIMS. This experimental approach led to significantly higher cluster concentrations than are normally found in ambient air, thereby increasing signal-to-noise levels and allowing us to study reactions between gas phase species in ambient air and sulfuric acid containing clusters. Mass peaks corresponding to clusters containing four H2SO4 molecules and one amine molecule were clearly observed, with the most abundant sulfuric acid-amine clusters being those containing a C2- or C4-amine (i.e. amines with masses of 45 and 73 amu). Evidence for C3- and C5-amines (i.e. amines with masses of 59 and 87 amu) was also found, but their correlation with sulfuric acid tetramer was not as strong as was observed for the C2- and C4-amines. The formation mechanisms for those sulfuric acid-amine clusters were investigated by varying the residence time in the inlet. It was concluded that the amines react directly with neutral clusters and that ion-induced clustering of sulfuric acid cluster ions with amines was not a dominant process. Results from ambient measurements using the Cluster CIMS without addition of sulfuric acid have shown that the sulfuric acid-amine clusters were reasonably well correlated with sulfuric acid tetramer and consistent with the SASA experiments at the same Boulder sampling site. Also, clusters that contain C2- or C4-amines were more abundant and better correlated with sulfuric acid tetramer than other types of amine containing clusters. However, ambient measurements of sulfuric acid-amine clusters remain difficult and highly uncertain because their concentrations are only slightly above background levels, even during nucleation events.

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18

Zhao, J., J. N. Smith, F. L. Eisele, M. Chen, C. Kuang i P. H. McMurry. "Observation of neutral sulfuric acid-amine containing clusters in laboratory and ambient measurements". Atmospheric Chemistry and Physics Discussions 11, nr 7 (11.07.2011): 19729–68. http://dx.doi.org/10.5194/acpd-11-19729-2011.

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Abstract. Recent ab initio calculations showed that amines can enhance atmospheric sulfuric acid-water nucleation more effectively than ammonia, and this prediction has been substantiated in laboratory measurements. Laboratory studies have also shown that amines can effectively displace ammonia in several types of ammonium clusters. However, the roles of amines in cluster formation and growth at a microscopic molecular scale (from molecular sizes up to 2 nm) have not yet been well understood. Processes that must be understood include the incorporation of amines into sulfuric acid clusters and the formation of organic salts in freshly nucleated particles, which contributes significantly to particle growth rates. We report the first laboratory and ambient measurements of neutral sulfuric acid-amine clusters using the Cluster CIMS, a recently-developed mass spectrometer designed for measuring neutral clusters formed in the atmosphere during nucleation. An experimental technique, which we refer to as Semi-Ambient Signal Amplification (SASA), was employed. Sulfuric acid was added to ambient air, and the concentrations and composition of clusters in this mixture were analyzed by the Cluster CIMS. This experimental approach led to significantly higher cluster concentrations than are normally found in ambient air, thereby increasing signal-to-noise levels and allowing us to study reactions between gas phase species in ambient air and sulfuric acid containing clusters. Mass peaks corresponding to clusters containing four H2SO4 molecules and one amine molecule were clearly observed, with the most abundant sulfuric acid-amine clusters being those containing a C2- or C4- amine (i.e., amines with masses of 45 and 73 amu). Evidence for C3- and C5- amines (i.e., amines with masses of 59 and 87 amu) was also found, but their correlation with sulfuric acid tetramer was not as strong as was observed for the C2- and C4- amines. The formation mechanisms for those sulfuric acid-amine clusters were investigated by varying the residence time in the inlet. It was concluded that the amines react directly with neutral clusters and that ion-induced clustering of sulfuric acid cluster ions with amines was not a dominant process. Results from ambient measurements have shown that the sulfuric acid-amine clusters were reasonably well correlated with sulfuric acid tetramer and consistent with the SASA experiments at the same Boulder sampling site. Also, clusters that contain C2- or C4- amines were more abundant and better correlated with sulfuric acid tetramer than other types of amine containing clusters. However, ambient measurements of sulfuric acid-amine clusters remain difficult and highly uncertain because their concentrations are only slightly above background levels, even during nucleation events.

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19

Liang, Dan, Wanting Shen, Chunfang Zhang, Pengfei Lu i Shumin Wang. "Structural, electronic, vibrational and optical properties of Bin clusters". Modern Physics Letters B 31, nr 28 (10.10.2017): 1750260. http://dx.doi.org/10.1142/s0217984917502608.

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The neutral, anionic and cationic bismuth clusters with the size n up to 14 are investigated by using B3LYP functional within the regime of density functional theory and the LAN2DZ basis set. By analysis of the geometries of the Bi[Formula: see text] (n = 2–14) clusters, where cationic and anionic bismuth clusters are largely similar to those of neutral ones, a periodic effect by adding units with one to four atoms into smaller cluster to form larger cluster is drawn for the stable structures of bismuth clusters. An even–odd alteration is shown for the properties of the clusters, such as the calculated binding energies and dissociation energies, as well as frontier orbital energies, electron affinities, ionization energies. All the properties indicate that the Bi4 cluster is the most possible existence in bismuth-containing materials, which supports the most recent experiment. The orbital compositions, infrared and Raman activities and the ultraviolet absorption of the most possible tetramer bismuth cluster are given in detail to reveal the periodic tendency of adding bismuth atoms and the stability of tetramer bismuth cluster.

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20

Yan, Jialin, Jingjing Xia, Qinfang Zhang, Binwen Zhang i Baolin Wang. "First-Principles Studies on the Structural and Electronic Properties of As Clusters". Materials 11, nr 9 (3.09.2018): 1596. http://dx.doi.org/10.3390/ma11091596.

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Based on the genetic algorithm (GA) incorporated with density functional theory (DFT) calculations, the structural and electronic properties of neutral and charged arsenic clusters Asn (n = 2–24) are investigated. The size-dependent physical properties of neutral clusters, such as the binding energy, HOMO-LUMO gap, and second difference of cluster energies, are discussed. The supercluster structures based on the As8 unit and As2 bridge are found to be dominant for the larger cluster Asn (n ≥ 8). Furthermore, the possible geometric structures of As28, As38, and As180 are predicted based on the growth pattern.

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21

Apostol, M., F. Rachdi, C. Goze i L. Hajji. "On sodium clusters in C60 fullerides". Canadian Journal of Chemistry 75, nr 1 (1.01.1997): 77–82. http://dx.doi.org/10.1139/v97-012.

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Sodium (Na) clusters in octahedral cages of Na-intercalated fullerides Na6C60 and Na11C60 are studied within a Thomas–Fermi model. It is shown that the tetrahedral Na4 cluster in Na6C60 has an electric charge ~ +2.7 (in electron charge units), while the body-centered cubic Na9 cluster in Na11C60 is almost electrically neutral. Keywords: sodium clusters, alkali fullerides, Thomas–Fermi theory, ionization charge.

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22

Francis, Paul J., Greg M. Wilson i Bruce E. Woodgate. "On the Gas Surrounding High-Redshift Galaxy Clusters". Publications of the Astronomical Society of Australia 18, nr 1 (2001): 64–75. http://dx.doi.org/10.1071/as01005.

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AbstractFrancis & Hewett (1993) identified two 10 Mpc-scale regions of the high-redshift universe that were seemingly very overdense in neutral hydrogen. Subsequent observations showed that at least one of these gas-rich regions enveloped a cluster of galaxies at redshift 2 ·38. We present improved observations of the three background QSOs with sightlines passing within a few Mpc of this cluster of galaxies. All three QSOs show strong neutral hydrogen absorption at the cluster redshift, suggesting that this cluster (and perhaps all high-redshift clusters) may be surrounded by a ~5 Mpc-scale region containing ~10 12 Mʘ of neutral gas. We show that if most high-redshift clusters are surrounded by such regions, the gas must be in the form of many small (<1 kpc), dense (> 0·03 cm ˗3 ) clouds, each of mass <10 6 Mʘ . These clouds are themselves probably gathered into >20 kpc-sized clumps, which may be galaxy halos or protogalaxies. If this gas exists, it will be partially photoionised by the UV background. We predict the diffuse Lyα flux from this photoionisation, and place observational limits on its intensity.

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23

SHOKRI, B., A. R. NIKNAM i V. KRAINOV. "Cluster structure effects on the interaction of an ultrashort intense laser field with large clusters". Laser and Particle Beams 22, nr 1 (marzec 2004): 13–18. http://dx.doi.org/10.1017/s0263034604221036.

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The structure of large clusters such as neutral clusters, metallic clusters, and clusters ion is investigated. Furthermore, the electron distribution of large clusters when they are irradiated by an intense ultrashort laser pulse is treated. The cluster excitation results from the interaction of the electron subsystem with the laser field. Analyzing the quantum metallic cluster proves that its properties differ essentially from the properties of a classical small metallic sphere. The eigen frequency of the surface oscillation of a cluster is obtained and it is shown that it is lower than Mie frequency because of Thomas–Fermi screening.

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24

Peng, Dong Liang, K. Sumiyama, H. Yamada, Takehiko Hihara i T. Uchida. "Preparation of Magnetically Soft, Highly-Densified Fe Cluster-Assembled Films by Impact Cluster Deposition". Advanced Materials Research 11-12 (luty 2006): 595–98. http://dx.doi.org/10.4028/www.scientific.net/amr.11-12.595.

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Highly-densified Fe cluster-assembled films were obtained at room temperature by an energetic cluster deposition. Fe clusters were produced using a plasma-gas-condensation (PGC)-type cluster deposition apparatus with a high cluster productivity. Ionized clusters in a cluster beam were electrically accelerated and directly deposited onto a substrate together with neutral clusters from the same cluster source. By increasing the impact energy of the ionized clusters up to about 1 eV/atom, the obtained cluster-assemblies have packing fractions higher than 0.8 without any serious size change, and result in a soft magnetic behavior up to a frequency range of few hundred MHz.

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25

Panov, I. V., i A. V. Yudin. "Light Neutral Clusters in Supernova Matter". Physics of Atomic Nuclei 82, nr 5 (wrzesień 2019): 483–90. http://dx.doi.org/10.1134/s1063778819040161.

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Díaz-Tendero, S., G. Sánchez, M. Alcamí, F. Martín, P. A. Hervieux, M. Chabot, G. Martinet i in. "Fragmentation of small neutral carbon clusters". International Journal of Mass Spectrometry 252, nr 2 (maj 2006): 126–32. http://dx.doi.org/10.1016/j.ijms.2005.12.055.

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27

Bachels, Thomas, i Rolf Schäfer. "Binding energies of neutral silicon clusters". Chemical Physics Letters 324, nr 5-6 (lipiec 2000): 365–72. http://dx.doi.org/10.1016/s0009-2614(00)00622-9.

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Buck, U. "Properties of Size Selected Neutral Clusters". Europhysics News 20, nr 4 (1989): 41–44. http://dx.doi.org/10.1051/epn/19892004041.

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29

Kerpal, C., D. J. Harding, G. Meijer i A. Fielicke. "CO adsorption on neutral iridium clusters". European Physical Journal D 63, nr 2 (17.12.2010): 231–34. http://dx.doi.org/10.1140/epjd/e2010-10480-8.

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Kerpal, Christian, Dan J. Harding, Jonathan T. Lyon, Gerard Meijer i André Fielicke. "N2 Activation by Neutral Ruthenium Clusters". Journal of Physical Chemistry C 117, nr 23 (3.06.2013): 12153–58. http://dx.doi.org/10.1021/jp401876b.

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Stanzel, Jörg, Emad F. Aziz, Matthias Neeb i Wolfgang Eberhardt. "Photoelectron Spectroscopy on Small Anionic Copper-Carbonyl Clusters". Collection of Czechoslovak Chemical Communications 72, nr 1 (2007): 1–14. http://dx.doi.org/10.1135/cccc20070001.

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Anion photoelectron spectroscopy in combination with density functional theory (DFT) calculations has been used to study mono- and dinuclear copper-carbonyl clusters Cun(CO)m- (n = 1, 2; m = 2-5). The adiabatic detachment energies of the anions have been measured which correspond to the electron affinities of the respective neutral species. The corresponding values are 0.95 eV for Cu(CO)2, 1.02 eV for Cu(CO)3, 1.04 eV for Cu(CO)4, 1.43 eV for Cu2(CO)4, and 1.19 eV for Cu2(CO)5. All spectra exhibit a pronounced vibrational fine structure on the adiabatic photodetachment peak. The energy splitting is close to the energy of the C-O stretching vibration of the neutral cluster (final state). The DFT calculations clearly indicate that in all clusters the highest occupied molecular orbital (HOMO) is a CO-derived π* orbital. Furthermore the calculations are used to give insight into geometry, frontier orbitals, vibrational frequencies and spin multiplicity of the neutral and anionic clusters.

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32

Liu, Y., S. Consta, F. Ogeer, Y. J. Shi i R. H. Lipson. "Geometries and energetics of methanol–ethanol clusters: a VUV laser/time-of-flight mass spectrometry and density functional theory study". Canadian Journal of Chemistry 85, nr 10 (1.10.2007): 843–52. http://dx.doi.org/10.1139/v07-104.

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Hydrogen-bonded clusters, formed above liquid methanol (Me) and ethanol (Et) mixtures of various compositions, were entrained in a supersonic jet and probed using 118 nm vacuum ultraviolet (VUV) laser single-photon ionization/time-of-flight mass spectrometry. The spectra are dominated by protonated cluster ions, formed by ionizing hydrogen-bonded MemEtn neutrals, m = 0–4, n = 0–3, and m + n = 2–5. The structures and energetics of the neutral and ionic species were investigated using both the all-atom optimized potential for liquid state, OPLS-AA, and the density functional (DFT) calculations. The energetic factors affecting the observed cluster distributions were examined. Calculations indicate that the large change in binding energy going from trimer to tetramer can be attributed more to pair-wise interactions than to cooperativity effects.Key words: alcohol clusters, cluster formation, DFT calculations, mass spectrometry, vacuum ultraviolet laser.

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33

Anagnastatos, G. S. "Light mixed alkali microclusters". HNPS Proceedings 3 (5.12.2019): 154. http://dx.doi.org/10.12681/hnps.2382.

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Wesendrup, Ralf, Tricia Hunt i Peter Schwerdtfeger. "Relativistic coupled cluster calculations for neutral and singly charged Au3 clusters". Journal of Chemical Physics 112, nr 21 (czerwiec 2000): 9356–62. http://dx.doi.org/10.1063/1.481556.

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35

Hautala, Lauri, Kari Jänkälä, Mikko-Heikki Mikkelä, Maxim Tchaplyguine i Marko Huttula. "Surface site coordination dependent responses resolved in free clusters: applications for neutral sub-nanometer cluster studies". Physical Chemistry Chemical Physics 17, nr 10 (2015): 7012–22. http://dx.doi.org/10.1039/c4cp05422a.

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36

Gobrecht, David, Jan Philip Sindel, Helena Lecoq-Molinos i Leen Decin. "The Ionization Energies of Dust-Forming Metal Oxide Clusters". Universe 7, nr 7 (14.07.2021): 243. http://dx.doi.org/10.3390/universe7070243.

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Stellar dust grains are predominantly composed of mineralic, anorganic material forming in the circumstellar envelopes of oxygen-rich AGB stars. However, the initial stage of the dust synthesis, or its nucleation, is not well understood. In particular, the chemical nature of the nucleating species, represented by molecular clusters, is uncertain. We investigated the vertical and adiabatic ionization energies of four different metal-oxide clusters by means of density functional theory. They included clusters of magnesia (MgO)n, silicon monoxide (SiO)n, alumina (Al2O3)n, and titania (TiO2)n with stoichiometric sizes of n = 1–8. The magnesia, alumina, and titania clusters showed relatively little variation in their ionization energies with respect to the cluster size n: 7.1–8.2 eV for (MgO)n, from 8.9–10.0 eV for (Al2O3)n, and 9.3–10.5 eV for (TiO2)n. In contrast, the (SiO)n ionization energies decrease with size n, starting from 11.5 eV for n = 1, and decreasing to 6.6 eV for n = 8. Therefore, we set constraints on the stability limit for neutral metal-oxide clusters to persist ionization through radiation or high temperatures and for the nucleation to proceed via neutral–neutral reactions.

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37

KATAKUSE, I., T. ICHIHARA, H. ITO, T. SAKURAI i T. MATSUO. "A NEW APPROACH OF THE SIMS METHOD FOR METAL CLUSTERS". Surface Review and Letters 03, nr 01 (luty 1996): 551–55. http://dx.doi.org/10.1142/s0218625x96001005.

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The size distributions of ( CsI )n Cs +, [Formula: see text], and [Formula: see text] (M: alkali metal, j=1, 2, 3, 4, 5) clusters were obtained using secondary-ion mass spectrometry. The sizes of stable neutral clusters ( CsI )n and ( Hg )n clusters were determined from the mass spectra of cluster ions ( CsI )n Cs + and ( Hg )nM+. The magic numbers of [Formula: see text] clusters were identical to those of van der Waals type clusters. It is believed that the shell closing cluster [Formula: see text] is at the center of complex clusters [Formula: see text]. The [Formula: see text] clusters were believed to have electronic shell structures from the magic numbers.

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38

Boreham, B. W., J. W. Waller, L. Cicchitelli, R. Khoda-Baksh, T. Rowlands i H. Hora. "Application of dense plasma beams to the development of a high-efficiency lateral injection laser amplifier". Laser and Particle Beams 11, nr 2 (czerwiec 1993): 443–53. http://dx.doi.org/10.1017/s0263034600005036.

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Recent developments in research on drivers for inertial confinement fusion identified the need to develop laser amplifiers with efficiencies of 80% or more. This article discusses a novel free electron laser amplifier that is based on vacuum interaction of laser beams with electrons, clusters of condensed matter, or neutral atoms. The scheme is based on the inversion of the ponderomotive expulsion of plasma from a focussed laser beam. The problem of Liouville conservation of phase space is overcome by employing the laser pulse transient processes. The optical energy for amplification is provided by the transfer of the translative kinetic energy of electrons, clusters, or neutral atoms that are injected nearly laterally into the laser pulse. The gains predicted to be achievable with this process are of interest for clusters, although the cluster densities presently available are too low to achieve the desired level of amplification. Neutral beams are shown to have the greatest potential for achieving large amplifications.

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39

Garcia, Jacob M., Ryan E. Shaffer i Scott G. Sayres. "Ultrafast pump–probe spectroscopy of neutral FenOm clusters (n, m < 16)". Physical Chemistry Chemical Physics 22, nr 42 (2020): 24624–32. http://dx.doi.org/10.1039/d0cp03889j.

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40

KAPLAN, I. G., R. SANTAMARÍA i O. NOVARO. "SIZE EFFECTS AND THE ROLE OF NONADDITIVE FORCES IN NEUTRAL AND ANIONIC SILVER-CLUSTER STABILITY". Surface Review and Letters 03, nr 01 (luty 1996): 235–39. http://dx.doi.org/10.1142/s0218625x96000462.

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The precise quantum-chemical study of neutral and anionic silver clusters manifests the pronounced size effect for the vertical ionization potential (VIP), vertical detachment energy (VDE), and atomic detachment energy (ε1). The additive and nonadditive contributions to the binding energy of clusters are calculated and their role in the cluster stability is discussed.

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41

Harmjanz, M., C. Junghans, U. A. Opitz, B. Bahlmann i S. Pohl. "Neue Synthesewege zu neutralen gemischtsubstituierten Eisen-Schwefel-Clustern / Novel Synthetic Pathways to Neutral Mixed-Ligand Iron-Sulfur Clusters". Zeitschrift für Naturforschung B 51, nr 7 (1.07.1996): 1040–48. http://dx.doi.org/10.1515/znb-1996-0722.

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The reaction of [Fe(NiSiMe3)2)2] with thiols RSH, elemental sulfur, and neutral ligands L (with sulfur donor atoms, e. g. thiourea derivatives) gives [Fe4S4(SR)2L2] clusters in high yields. The structure of [Fe4S4(2.4.6-(C3H7)3C6H2-S)2(dpdmi)2] (dpdmi: diisopropyldimethyl- imidazolthion) was determined by X-ray crystallography.When [Fe4S4I4]2- is reacted with a large excess of PMePh2 or PMe2Ph [F6S6I2(PMePh2)4] and [Fe6S6l2(PMe2Ph)4]. respectively, are obtained in nearly quantitative yield. Basket-like structures of the [Fe6S6]2+ cores were detected by X-ray structure analysis. While [Fe4S4(SR)4]2- clusters do not react with phosphanes at ambient temperature 2:2 functionalized species like [Fe4S4(SR)2(tmtu)2] lead to basket-type clusters [Fe6S6(SR)2(PR3)4].

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42

Kontkanen, J., K. E. J. Lehtinen, T. Nieminen, H. E. Manninen, K. Lehtipalo, V. M. Kerminen i M. Kulmala. "Estimating the contribution of ion–ion recombination to sub-2 nm cluster concentrations from atmospheric measurements". Atmospheric Chemistry and Physics Discussions 13, nr 8 (9.08.2013): 20809–37. http://dx.doi.org/10.5194/acpd-13-20809-2013.

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Abstract. The significance of ion–ion recombination for atmospheric new particle formation is not well quantified. Here we present and evaluate a method for determining the size distribution of recombination products from the size distributions of neutral and charged clusters. We applied this method to the data measured in Hyytiälä, Finland, to estimate the contribution of ion–ion recombination to the concentrations of atmospheric clusters in the size range of 0.9–2.1 nm. We observed that the concentration of recombination products was highest in the size classes between 1.5 and 1.9 nm. The median concentrations of recombination products were between 1 and 79 cm−3 in different size classes, which resulted in a small proportion of all neutral clusters, varying between 0.05% and 15%. When examining the whole size range between 0.9 and 2.1 nm, the median fraction of recombination products of all neutral clusters was only 1.5%. Overall, the applied method was concluded to be reasonable, and the results are consistent with the earlier estimates on the contribution of recombination products to atmospheric cluster population in Hyytiälä. Still, in order to determine the size distribution of recombination products more accurately in the future, more precise measurements of the size distribution of sub-2 nm clusters would be needed.

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43

RAYNER, D. M., L. LIAN, S. A. MITCHELL i P. A. HACKETT. "GAS-PHASE CHEMISTRY OF MOLYBDENUM CLUSTERS". Surface Review and Letters 03, nr 01 (luty 1996): 675–78. http://dx.doi.org/10.1142/s0218625x96001212.

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The kinetics of reactions of molybdenum clusters, Mo n, n=1–25, in the pressure range 0.4–4 Torr, and temperature range 270–380 K, have been investigated using a large-bore, He-buffered, fast-flow reactor equipped with a laser-vaporization source for the production of clusters. The reactor is designed to make kinetic measurements on neutral metal clusters in the gas phase under well-defined pressures and temperatures. We discuss a new version of the instrument in which LIF techniques, used previously to monitor atoms and dimers, are replaced by laser ionization, time-of-flight mass spectrometry (TOFMS) in order to monitor larger clusters. The new version of the reactor has been tested against known reactions of Ti atoms. Examples of the reactor’s performance are taken from studies performed on Mon cluster reactivity. In particular we summarize some results on the dissociative chemisorption of molecular nitrogen, where large cluster-size effects are found. In some cases a negative-temperature dependence of the kinetics indicates the involvement of a precursor bound state and leads to conclusions concerning the shape of the potential-energy surface and how subtle changes associated with the cluster’s geometric structure might profoundly alter reaction rates.

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44

Manninen, Hanna E., Sander Mirme, Aadu Mirme, Tuukka Petäjä i Markku Kulmala. "How to reliably detect molecular clusters and nucleation mode particles with Neutral cluster and Air Ion Spectrometer (NAIS)". Atmospheric Measurement Techniques 9, nr 8 (3.08.2016): 3577–605. http://dx.doi.org/10.5194/amt-9-3577-2016.

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Abstract. To understand the very first steps of atmospheric particle formation and growth processes, information on the size where the atmospheric nucleation and cluster activation occurs, is crucially needed. The current understanding of the concentrations and dynamics of charged and neutral clusters and particles is based on theoretical predictions and experimental observations. This paper gives a standard operation procedure (SOP) for Neutral cluster and Air Ion Spectrometer (NAIS) measurements and data processing. With the NAIS data, we have improved the scientific understanding by (1) direct detection of freshly formed atmospheric clusters and particles, (2) linking experimental observations and theoretical framework to understand the formation and growth mechanisms of aerosol particles, and (3) parameterizing formation and growth mechanisms for atmospheric models. The SOP provides tools to harmonize the world-wide measurements of small clusters and nucleation mode particles and to verify consistent results measured by the NAIS users. The work is based on discussions and interactions between the NAIS users and the NAIS manufacturer.

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45

Rose, C., K. Sellegri, E. Asmi, M. Hervo, E. Freney, H. Junninen, J. Duplissy i in. "Major contribution of neutral clusters to new particle formation in the free troposphere". Atmospheric Chemistry and Physics Discussions 14, nr 12 (10.07.2014): 18355–88. http://dx.doi.org/10.5194/acpd-14-18355-2014.

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Abstract. The formation of new aerosol particles in the atmosphere is a key process influencing the aerosol number concentration as well as the climate, in particular in the free troposphere (FT) where the newly formed particles directly influence cloud formation. However, free tropospheric new particle formation (NPF) is poorly documented due to logistic limitations and complex atmospheric dynamics around high altitude stations that make the observation of this day-time process challenging. Recent improvements in measurement techniques make now possible the detection of neutral clusters down to ~ 1 nm sizes, which opens new horizons in our understanding of the nucleation process. Indeed, only the charged fraction of clusters has been reported in the upper troposphere up to now. Here we report observations of charged and neutral clusters (1 to 2.5 nm mobility diameter) during day-time free tropospheric conditions at the altitude site of Puy de Dôme (1465 m a.s.l.), central France, between 10 and 29 February 2012. Our findings demonstrate that in the free troposphere, the formation of 1.5 nm neutral clusters is about 40 times higher than the one of ionic clusters during NPF events, indicating that they dominate in the nucleation process. We also observe that the total cluster concentration increases by a factor of 5.5 during NPF events compared to the other days, which was not clearly observed for the charged cluster population in the past. In the FT, the nucleation process does not seem to be sulphuric acid-limited, as previously suggested, and could be promoted by the transport of pollutants to the upper troposphere.

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46

Jorge, Francisco E., i Luiz G. M. de Macedo. "Dipole (hyper)polarizabilities of neutral silver clusters". Chinese Physics B 25, nr 12 (29.11.2016): 123102. http://dx.doi.org/10.1088/1674-1056/25/12/123102.

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47

Haertelt, Marko, Jonathan T. Lyon, Pieterjan Claes, Jorg de Haeck, Peter Lievens i André Fielicke. "Gas-phase structures of neutral silicon clusters". Journal of Chemical Physics 136, nr 6 (14.02.2012): 064301. http://dx.doi.org/10.1063/1.3682323.

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Kolenbrander, K. D., i M. L. Mandich. "Electronic spectroscopy of neutral indium phosphide clusters". Journal of Chemical Physics 90, nr 10 (15.05.1989): 5884–85. http://dx.doi.org/10.1063/1.456399.

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49

OBI, Kinichi, i Kazuhiko SHIBUYA. "Generation and Photochemical Reaction of Neutral Clusters." Hyomen Kagaku 14, nr 4 (1993): 192–98. http://dx.doi.org/10.1380/jsssj.14.192.

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50

Ma, Z., S. R. Coon, W. F. Calaway, M. J. Pellin, D. M. Gruen i E. I. von Nagy‐Felsobuki. "Sputtering of neutral and ionic indium clusters". Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films 12, nr 4 (lipiec 1994): 2425–30. http://dx.doi.org/10.1116/1.579185.

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