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Journal articles on the topic 'Hyperfine transitions'

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Published: 4 June 2021

Last updated: 28 January 2023

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1

Tong, Xi, Yi Wang, and Hui-Yu Zhu. "Gravitational Collider Physics via Pulsar–Black Hole Binaries II: Fine and Hyperfine Structures Are Favored." Astrophysical Journal 924, no. 2 (January 1, 2022): 99. http://dx.doi.org/10.3847/1538-4357/ac36db.

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Abstract A rotating black hole can be clouded by light bosons via superradiance and thus acquire an atom-like structure. If such a gravitational atom system is accompanied by a pulsar, the pulsar can trigger transitions between energy levels of the gravitational atom, and these transitions can be detected by pulsar timing. We show that in such pulsar–black hole systems, fine and hyperfine structure transitions are more likely to be probed than the Bohr transition. Also, the calculation of these fine and hyperfine structure transitions are under better analytic control. Thus, these fine and hyperfine structure transitions are more ideal probes in the search for gravitational collider signals in pulsar–black hole systems.

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2

Gould, Robert J. "Radiative hyperfine transitions." Astrophysical Journal 423 (March 1994): 522. http://dx.doi.org/10.1086/173830.

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3

Garstang, R. H. "Radiative Hyperfine Transitions." Astrophysical Journal 447 (July 1995): 962. http://dx.doi.org/10.1086/175933.

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4

Brill, A. S. "Hyperfine interactions in H2N." Canadian Journal of Physics 86, no. 6 (June 1, 2008): 767–81. http://dx.doi.org/10.1139/p07-205.

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All of the hyperfine interactions associated with localized and delocalized electron spin in the four isotopes of the triatomic radical H2N are treated. With nuclear Zeeman energy included, the resulting magnetic-field-dependent nuclear spin states are used to calculate the energies and nuclear spin-state mixing of the nuclear levels and the corresponding hyperfine effects upon electron paramagnetic resonance (EPR) transition energies and nuclear state transition probabilities. In the absence of nuclear spin-state mixing there would be, for example, 10 EPR transitions in D2 15N and 15 in D2 14N, all ΔmI = 0 fully allowed. In the presence of mixing, there are 243 in D2 15N and 729 in D2 14N, with large differences in probability among transitions, many 0 or small. Because of numerous (at least partially allowed) transitions, spectra from isotopes of H2 N radicals are the superposition of signals at greatly different levels of saturation. In this report, EPR spectra from D2 15N models, with either N or 2D hyperfine interaction suppressed, are simulated as a function of microwave frequency and power × spin-lattice relaxation time product. A large range of microwave frequency (and, concomitantly, magnetic field strength) will be needed to evaluate the effect of the nuclear Zeeman energy. The experimental requirements for microwave power and low temperature (long spin-lattice relaxation rate) are quantified.PACS Nos.: 33.15.Pw, 33.35.+r, 33.25.+k

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5

Dall’Olio, D., W. H. T. Vlemmings, B. Lankhaar, and G. Surcis. "Polarisation properties of methanol masers." Astronomy & Astrophysics 644 (December 2020): A122. http://dx.doi.org/10.1051/0004-6361/202039149.

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Context. Astronomical masers have been effective tools in the study of magnetic fields for years. Observations of the linear and circular polarisation of different maser species allow for the determination of magnetic field properties, such as morphology and strength. In particular, methanol can be used to probe different parts of protostars, such as accretion discs and outflows, since it produces one of the strongest and the most commonly observed masers in massive star-forming regions. Aims. We investigate the polarisation properties of selected methanol maser transitions in light of newly calculated methanol Landé g-factors and in consideration of hyperfine components. We compare our results with previous observations and evaluate the effect of preferred hyperfine pumping and non-Zeeman effects. Methods. We ran simulations using the radiative transfer code, CHAMP, for different magnetic field values, hyperfine components, and pumping efficiencies. Results. We find a dependence between the linear polarisation fraction and the magnetic field strength as well as the hyperfine transitions. The circular polarisation fraction also shows a dependence on the hyperfine transitions. Preferred hyperfine pumping can explain some high levels of linear and circular polarisation and some of the peculiar features seen in the S-shape of observed V-profiles. By comparing a number of methanol maser observations taken from the literature with our simulations, we find that the observed methanol masers are not significantly affected by non-Zeeman effects related to the competition between stimulated emission rates and Zeeman rates, such as the rotation of the symmetry axis. We also consider the relevance of other non-Zeeman effects that are likely to be at work for modest saturation levels, such as the effect of magnetic field changes along the maser path and anisotropic resonant scattering. Conclusions. Our models show that for methanol maser emission, both the linear and circular polarisation percentages depend on which hyperfine transition is masing and the degree to which it is being pumped. Since non-Zeeman effects become more relevant at high values of brightness temperatures, it is important to obtain good estimates of these quantities and the maser beaming angles. Better constraints on the brightness temperature will help improve our understanding of the extent to which non-Zeeman effects contribute to the observed polarisation percentages. In order to detect separate hyperfine components, an intrinsic thermal line width that is significantly smaller than the hyperfine separation is required.

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6

Dagdigian, Paul J. "Collisional excitation of the formyl radical (HCO) by molecular hydrogen." Monthly Notices of the Royal Astronomical Society 498, no. 4 (September 14, 2020): 5361–66. http://dx.doi.org/10.1093/mnras/staa2803.

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ABSTRACT This paper addresses the need for accurate rate coefficients for transitions between fine- and hyperfine-structure resolved rotational transitions in the formyl (HCO) radical induced by collisions with the two nuclear spin modifications of H2, the dominant molecule in the interstellar medium (ISM). These rate coefficients, as well as radiative transition rate coefficients, are required for accurate determination of the abundance of HCO in the ISM. Time-independent close-coupling quantum scattering calculations have been used to compute rate coefficients for (de-)excitation of HCO in collisions with para- and ortho-H2. These calculations utilized a potential energy surface for the interaction of HCO with H2 recently computed by the explicitly correlated RCCSD(T)-F12a coupled-cluster method. Rate coefficients for temperatures ranging from 5 to 400 K were calculated for all transitions among the fine and hyperfine levels associated with the first 22 rotational levels of HCO, whose energies are less than or equal to 144 K.

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7

Wiklind, T., and F. Combes. "Limits on the Variation of Physical Constants Derived from Molecular Absorption Lines." Symposium - International Astronomical Union 183 (1999): 167. http://dx.doi.org/10.1017/s0074180900132474.

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A potential diagnostic application of molecular rotational absorption lines at high redshift is to test the invariance of physical constants. This can be done by comparing the observed redshifted frequency of a molecular absorption line with redshifted lines from other types of transitions such as the 21cm hyperfine transition or electronic resonance transitions. In order to set stringent limits, it is necessary to achieve the greatest possible frequency resolution. This makes radio lines well suited for this purpose.

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8

Ahrens, Volker, Frank Lewen, Shuro Takano, Gisbert Winnewisser, Štepán Urban, A. A. Negirev, and A. N. Koroliev. "Sub-Doppler Saturation Spectroscopy of HCN up to 1 THz and Detection of J = 3 —> 2 (4—> 3) Emission from TMC1." Zeitschrift für Naturforschung A 57, no. 8 (August 1, 2002): 669–81. http://dx.doi.org/10.1515/zna-2002-0806.

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Very high-resolution ( ∼ 30 kHz) and very precise (±2 kHz) saturation dip and crossover dip measurements are reported for HCN. Nine consecutive rotational transitions of the vibrational ground state were recorded, covering the rotational spectrum up to the J = 11 ← 10 transition at 975 GHz. Commencing the saturation dip measurements with the J = 3 ← 2 transition located at 265 886.4 MHz, all rotational transitions were measured up to J = 11 ← 10 (ΔF = 1), positioned at a center frequency of 974 487.2 MHz. It has become possible to resolve the hyperfine structure of every rotational transition to varying degrees. Transitions obeying the selection rules ΔJ = 1, ΔF = 0 are have been resolved, those obeying the selection rules J = 1, F = 1 are only resolved for transitions lower than the J = 6 ← 5 transition.These new experimental saturation dip data, together with the molecular beam maser emission data of the J = 1 → 0 and J = 2 → 1 transitions reported by De Lucia and Gordy, (Phys. Rev. 187, 58 (1969)), and the recent terahertz measurements performed in this laboratory up to J = 22-21 at 1.946 THz (Maiwald et al., J. Mol. Spectrosc. 202, 166 (2000)), were subjected to a least squares analysis which yielded a highly precise set of molecular constants for the ground state of HCN: B = 44 315.974 970 (156) MHz, D = 0.087 216 35 (169) MHz, H = 0.086 96 (242) Hz; eQq = -4.709 03 (162) MHz, eQqJ = 0.244 (88) Hz, CN = 10.09 (38) kHz, CNJ = -0.0143 (86) mHz. Two constants, the hydrogen spin-rotation, CH = -4.35 (5) kHz, and the spin-spin interaction between the proton and nitrogen nucleus, SNH = 0.154 (3) kHz, can not be determined from the saturation dip measurements and have been taken from Ebenstein and Muenter, J. Chem. Phys. 80, 3989 (1984). There also a value for the ground state permanent electric dipole moment (in Debye’s) is given, which we quote for completeness: 〈μ〉000 = 2.985 188 (3) D. We also report the discovery of the J = 3 → 2 and J = 4 → 3 ground state rotational transitions of HCN in the dark, cold molecular cloud TMC1 by using the KOSMA 3m-Submillimeter Telescope located in the central Swiss Alps. For the J = 3 → 2 transition the hyperfine splitting has partly been resolved. The intensities of the hyperfine components are anomalous, and they are not in thermodynamic equilibrium.

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9

Alhasan, Abu Mohamed. "Graph Entropy Associated with Multilevel Atomic Excitation." Proceedings 46, no. 1 (March 14, 2020): 9. http://dx.doi.org/10.3390/ecea-5-06675.

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A graph-model is presented to describe multilevel atomic structure. As an example, we take the double Λ configuration in alkali-metal atoms with hyperfine structure and nuclear spin I = 3 / 2 , as a graph with four vertices. Links are treated as coherence. We introduce the transition matrix which describes the connectivity matrix in static graph-model. In general, the transition matrix describes spatiotemporal behavior of the dynamic graph-model. Furthermore, it describes multiple connections and self-looping of vertices. The atomic excitation is made by short pulses, in order that the hyperfine structure is well resolved. Entropy associated with the proposed dynamic graph-model is used to identify transitions as well as local stabilization in the system without invoking the energy concept of the propagated pulses.

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10

Barducci, A., R. Giachetti, and E. Sorace. "Relativistic two fermion treatment of hyperfine transitions." Journal of Physics B: Atomic, Molecular and Optical Physics 48, no. 8 (March 31, 2015): 085002. http://dx.doi.org/10.1088/0953-4075/48/8/085002.

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11

Misra, Sushil K., and Changlu Wang. "EPR ofVO2+-dopedK2C2O4⋅H2O: Forbidden hyperfine transitions." Physical Review B 39, no. 13 (May 1, 1989): 8832–44. http://dx.doi.org/10.1103/physrevb.39.8832.

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12

Flower, D. R., and P. Hily-Blant. "Hyperfine transitions of13CN from pre-protostellar sources." Monthly Notices of the Royal Astronomical Society 452, no. 1 (July 1, 2015): 19–23. http://dx.doi.org/10.1093/mnras/stv1322.

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13

Kolbinger, B., A. Capon, M. Diermaier, S. Lehner, C. Malbrunot, O. Massiczek, C. Sauerzopf, M. C. Simon, and E. Widmann. "Numerical simulations of hyperfine transitions of antihydrogen." Hyperfine Interactions 233, no. 1-3 (February 4, 2015): 47–51. http://dx.doi.org/10.1007/s10751-015-1130-3.

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14

Doppelbauer, M., S. C. Wright, S. Hofsäss, B. G. Sartakov, G. Meijer, and S. Truppe. "Hyperfine-resolved optical spectroscopy of the A²Π ← X²Σ⁺ transition in MgF." Journal of Chemical Physics 156, no. 13 (April 7, 2022): 134301. http://dx.doi.org/10.1063/5.0081902.

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We report on hyperfine-resolved laser spectroscopy of the A2Π ← X2Σ+ transition of magnesium monofluoride (MgF), relevant for laser cooling. We recorded 25 rotational transitions with an absolute accuracy of better than 20 MHz, assigned 56 hyperfine lines, and determined precise rotational, fine, and hyperfine structure parameters for the A2Π state. The radiative lifetime of the A2Π state was determined to be 7.2(3) ns, in good agreement with ab initio calculations. The transition isotope shift between bosonic isotopologues of the molecule is recorded and compared to predicted values within the Born–Oppenheimer approximation. We measured the Stark effect of selected rotational lines of the A2Π ← X2Σ+ transition by applying electric fields of up to 10.6 kV cm−1 and determined the permanent electric dipole moments of 24MgF in its ground X2Σ+ and first excited A2Π states to be μ X = 2.88(20) D and μ A = 3.20(22) D, respectively. Based on these measurements, we caution for potential losses from the optical cycling transition due to electric field induced parity mixing in the excited state. In order to scatter 104 photons, the electric field must be controlled to below 1 V cm−1.

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15

Preusser, Jürgen, and Manfred Winnewisser. "Nuclear Quadrupole Hyperfine Structure of the Direct /-Type Transitions of the Fulminic Acid Isotopomers H12C14N16O and H13C14N16O." Zeitschrift für Naturforschung A 51, no. 3 (March 1, 1996): 207–14. http://dx.doi.org/10.1515/zna-1996-0313.

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The direct I- type transitions of H133C14N16O in the vibrational states (υ4,υ5) = (01) and (03) were measured in the frequency range from 18 to 40 GHz. These transitions show a nuclear quadrupole hyperfine structure caused by the 14N nucleus, which could partially be resolved at Doppler-limited resolution. The analogous transitions of the parent species. H12C14N16O, were remeasured. They displayed a very similar hyperfine structure, also partially resolved. The hyperfine patterns of both H12C14N16O and H13C14N16O were analysed by means of contour fitting s to the absorption profiles. The parameter ηseQq, which is responsible for the splittings, is determined to be 645(20) kHz for the vibrational state (01) and 890(44) kHz for the vibrational state (03) for H12C14N16O and 642(32) kHz for (01) and 898(22) kHz for (03) for H13C14N16O. This unexpectedly large splitting parameter for states involving the large amplitude motion υ5 (HCN bending) is discussed as another consequence of the quasilinearity of fulminic acid, in view of the fact that the analogous transitions for the vibrational state (10) (NCO bending) do not split or even show a significant line broadening at the resolution used for the present measurements

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16

Саргсян, А., Т. А. Вартанян, and Д. Саркисян. "Исследование взаимодействия атомов Cs с поверхностью сапфира с использованием сверхтонкой ячейки и метода вычисления второй производной спектра поглощения паров." Журнал технической физики 128, no. 5 (2020): 589. http://dx.doi.org/10.21883/os.2020.05.49313.6-20.

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The influence of the interaction of Cs atoms with a dielectric surface on the position and shape of the hyperfine components of the D2 line at nanometer-order distances between atoms and the surface is studied. The use of a nanocell with a wedge-shaped gap made it possible to study the dependence of the shifts of all the hyperfine components of the D2 line corresponding to the transitions Fg = 3- Fe = 2, 3, 4 and Fg = 4- Fe = 3, 4, 5, on the distance L between the atoms and the sapphire surface windows in the range of 50–400 nm. At L less than 100 nm, due to the van der Waals interaction, there is a strong broadening of atomic transitions and a shift of their frequencies to the low-frequency region of the spectrum (red shift). The calculation of the second derivative (SD) of the vapor absorption spectra in the nanocell allows one to spectrally resolve the hyperfine components of the atomic transition down to L about 50 nm and measure the coefficient of the van der Waals interaction C3. It is shown that, at L <100 nm, an additional red shift occurs with increasing atomic density, while at relatively large distances between atoms and the surface L about 400 nm, an increase in atomic density causes a blue shift of the atomic transition frequencies. The above results are important in the development of miniature submicron devices containing atomic vapor of alkali metal.

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17

UDOMKAN, NITINAI, and PICHET LIMSUWAN. "ARAGONITE TO CALCITE TRANSFORMATION STUDIES BY ESR OF Mn2+ IONS IN SINOTAIA INGALLSIANA." Modern Physics Letters B 23, no. 09 (April 10, 2009): 1243–47. http://dx.doi.org/10.1142/s0217984909019375.

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We have studied paramagnetic Mn 2+ ions present in the freshwater snail, Sinotaia ingallsiana (FS), Viviparus which are abundant in Thailand. The FS shells in our study were ground into fine powder. A set of seven samples was each then separately annealed for 2 hours in air atmosphere at 300°C, 400°C, 500°C, 600°C, 700°C, 800°C and 900°C, respectively. Our detailed ESR spectral analyses of FS show that Mn 2+ ions enter Ca 2+ sites during a biomineralization process. The hyperfine coupling constant (A) and zero-field splitting (D) in the ESR spectrum of Mn 2+ in calcite and aragonite were determined. The spreading of the non-central allowed transitions was analyzed and the experimental transitions were attributed. For calculating the hyperfine coupling constant, five methods for calculating the zero-field splitting, based on the analysis of the allowed and forbidden transitions, were provided. The values of the hyperfine coupling constant range from 87.50 to 89.00 G and those of the zero-field splitting range from 110.00 to 116.00 G.

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18

BARTOS, A., D. WIARDA, Z. INGLOT, K. P. LIEB, M. UHRMACHER, and T. WENZEL. "MAGNETIC PHASE TRANSITIONS IN TRANSITIONAL METAL OXIDES STUDIED WITH PERTURBED ANGULAR CORRELATIONS." International Journal of Modern Physics B 07, no. 01n03 (January 1993): 357–60. http://dx.doi.org/10.1142/s0217979293000755.

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The Perturbed Angular Correlation (PAC) method with radioactive tracer nuclei is well-suited to study the critical behaviour of magnetic hyperfine fields. Here we present the results of PAC measurements with 111 Cd probes, concerning the antiferromagnetic phase transitions in CuO, Co 3 O 4 and MnO. The measured Larmor frequencies were fitted with a Curie-Weiss type temperature dependence ωL (T) /ωL(0) = (1- T/T N)β. In CuO the PAC probe is subject to a high electric field gradient (efg) with the coupling constant νQ = 434(2) MHz and the asymmetry parameter η = 0.42(1). Therefore, combined electric/magnetic hyperfine interaction is observed below T N. Similar to neutron diffraction experiments, a second magnetic transition was observed at T 1 = 213 K . The analysis of the PAC data gave T N = 224(2) K and β = 0.33(1) for T 1 ≤ T ≤ T N. In the spinel Co 3 O 3, the measured critical parameters for 111 Cd at cation sites with tetrahedral oxygen coordination are T N = 39(1) K and β = 0.34(2). This site has a nearly cubic oxygen coordination and therefore a vanishing efg. In Mn 1−x O (defective NaCl structure, x ≤ 0.15), the critical parameters were found to sensitively depend on the annealing conditions. They will be discussed in comparison with those in Fe 1−x O .

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19

Rosner, S. D., D. Masterman, T. J. Scholl, and R. A. Holt. "Measurement of hyperfine structure and isotope shifts in Nd II." Canadian Journal of Physics 83, no. 8 (August 1, 2005): 841–54. http://dx.doi.org/10.1139/p05-029.

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The high-resolution spectra of 110 transitions in Nd II over the range 418465 nm were observed using the collinear fast-ion-beam/laser method (FIBLAS). The lower states of these transitions include the ground state and 10 metastable even-parity states with energies up to 5986 cm1. The 64 odd-parity upper states have energies up to 29 434 cm1. For each transition isotope shifts were measured for all the stable isotopes (mass numbers 142, 143, 144, 145, 146, 148, and 150), as well as hyperfine parameters for the two odd-mass-number isotopes. These quantities are important in modeling profiles of absorption lines in stellar atmospheres to obtain abundances, and in the classification of atomic energy levels. PACS Nos.: 31.30.Gs, 32.10.Fn, 95.30.Ky

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20

Brünken, S., E. A. Michael, F. Lewen, Th Giesen, H. Ozeki, G. Winnewisser, P. Jensen, and E. Herbst. "High-resolution terahertz spectrum of CH2 Low J rotational transitions near 2 THz." Canadian Journal of Chemistry 82, no. 6 (June 1, 2004): 676–83. http://dx.doi.org/10.1139/v04-034.

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The methylene radical (CH2) was very important to Gerhard Herzberg. We have carried out high-resolution spectroscopic measurements on two energetically low-lying, pure rotational transitions of methylene in its ground vibrationalelectronic state at frequencies near 2 THz. One of the transitions the NKaKc = 211 ← 202 multiplet belongs to ortho-CH2 and is centered at 1.954 THz. The other rotational transition the NKaKc = 110 ← 101 multiplet belongs to para-CH2 and is centered at 1.915 THz. Since the ground electronic state of methylene has 3B1 symmetry, the rotational transitions are split into three fine-structure components, while the ortho transitions are split additionally by hyperfine structure. In total, we have measured 29 new lines, six for the para transition and the remainder for the ortho transition. The newly measured lines can be added to high-resolution spectral data obtained by ourselves and others at lower frequencies. Progress towards a global fit is discussed. Key words: spectroscopy, THz frequencies, radicals, methylene, interstellar medium.

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21

Dagdigian, Paul J. "Collisional excitation of deuterated hydroxyl (OD) by molecular hydrogen." Monthly Notices of the Royal Astronomical Society 505, no. 2 (May 19, 2021): 1987–91. http://dx.doi.org/10.1093/mnras/stab1412.

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ABSTRACT Cross sections and rate coefficients for transitions between hyperfine levels associated with the 14 lowest rotational/fine-structure levels of OD induced by collisions with ortho-H2 and para-H2 are presented. These collisional parameters have been computed in time-independent close-coupling quantum-scattering calculations with a potential energy surface (PES) describing the OD–H2 interaction, which was obtained by transformation of the OH–H2 PES. Rate coefficients have been computed for temperatures from 5 to 200 K. Cross sections for OD transitions between rotational/fine-structure levels are found to be significantly larger than the corresponding transitions in OH, mainly because of the reduced energy gaps in OD. The hyperfine-resolved rate coefficients were employed in simple radiative transfer calculations for OD and compared with analogous calculations for OH.

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22

Jóźwiak, Hubert, Hubert Cybulski, and Piotr Wcisło. "Hyperfine structure of rovibrational quadrupole transitions in HD." Journal of Quantitative Spectroscopy and Radiative Transfer 272 (September 2021): 107753. http://dx.doi.org/10.1016/j.jqsrt.2021.107753.

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23

Sampson, D. H., and H. L. Zhang. "Collision strengths for hyperfine-structure transitions: application to." Journal of Physics B: Atomic, Molecular and Optical Physics 30, no. 6 (March 28, 1997): 1449–56. http://dx.doi.org/10.1088/0953-4075/30/6/013.

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24

Monteiro, T. S., and J. Stutzki. "Collisional excitation of the hyperfine transitions of HCN." Monthly Notices of the Royal Astronomical Society 221, no. 1 (July 1986): 33P—39P. http://dx.doi.org/10.1093/mnras/221.1.33p.

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25

Atherton, P. S., B. J. Dalton, and I. R. Dagg. "Autler-Townes doublets in the hyperfine transitions of14NH3." Journal of Physics B: Atomic and Molecular Physics 19, no. 3 (February 14, 1986): 277–92. http://dx.doi.org/10.1088/0022-3700/19/3/011.

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26

Chukalina, E. P., and M. N. Popova. "Hyperfine structure of infrared transitions in LiYF4:Er3+." Physics Letters A 262, no. 2-3 (November 1999): 191–94. http://dx.doi.org/10.1016/s0375-9601(99)00687-8.

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27

Martin, J. P. D., T. Boonyarith, N. B. Manson, Y. L. Khong, and G. D. Jones. "Strain broadening of optical transitions with hyperfine structure." Physical Review B 49, no. 22 (June 1, 1994): 15495–97. http://dx.doi.org/10.1103/physrevb.49.15495.

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28

Vermeeren, L., P. Lievens, and R. E. Silverans. "Sensitive laserspectroscopy on ions with hyperfine split transitions." Hyperfine Interactions 61, no. 1-4 (August 1990): 1399–402. http://dx.doi.org/10.1007/bf02407635.

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29

McCammon, C. A. "Applications of 61Ni Mössbauer spectroscopy." Canadian Journal of Physics 65, no. 10 (October 1, 1987): 1294–300. http://dx.doi.org/10.1139/p87-204.

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The number of 61Ni Mössbauer studies, although small, indicates that definitive measurements are possible once experimental obstacles have been overcome. The experimental method and hyperfine interactions in 61Ni are discussed briefly, followed by a review of results obtained from 61Ni Mössbauer experiments during the last 10 years. The results are discussed in relation to the determination of spin structures, the study of electronic transitions, and the study of hyperfine interactions.

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30

Marinakis, S., Y. Kalugina, J. Kłos, and F. Lique. "Hyperfine excitation of CH and OH radicals by He." Astronomy & Astrophysics 629 (September 2019): A130. http://dx.doi.org/10.1051/0004-6361/201936170.

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Context. Because of their high reactivity, the CH and OH radicals are of particular interest in astrochemistry. Modeling of CH and OH molecules requires the calculation of accurate radiative Einstein coefficients and rate coefficients for (de)excitation by collisions with the most abundant species such as H2 and He. Aims. The present paper focuses on the calculation of inelastic rate coefficients among the lowest OH/CH hyperfine levels in their ground vibrational state induced by collisions with He atoms. Methods. Calculations of hyperfine (de)excitation of CH/OH by He were performed using the close-coupling and recoupling methods from the most recent ab initio potential energy surfaces. Results. Cross sections for transitions among the 60 and 56 lowest hyperfine levels of CH and OH, respectively, were calculated for collision energies up to 2500 cm−1. These cross-sections were used to calculate the rate coefficients for temperatures between 10 and 300 K. A propensity rule for transitions with ΔF = Δj was observed. Conclusions. The new rate coefficients will help significantly in interpreting the CH/OH spectroscopic data observed with current and future telescopes, and help to accurately describe the OH masers and the hyperfine anomalies in CH emission spectra.

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31

Ndaw, D., C. T. Bop, G. Dieye, N. A. Boye Faye, and F. Lique. "The excitation of CNCN in the interstellar medium: hyperfine resolved rate coefficients and non-LTE modelling." Monthly Notices of the Royal Astronomical Society 503, no. 4 (March 18, 2021): 5976–83. http://dx.doi.org/10.1093/mnras/stab775.

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ABSTRACT The recent detections of CNCN and HNCCN+ are seen as further evidence of the large abundance of NCCN in the interstellar medium. The accurate determination of the abundance of these chemically related compounds from the observational spectra requires the prior calculation of collisional rate coefficients. In this work, we aimed at computing hyperfine resolved rate coefficients for the CNCN–He collisional system. First, we determined a new potential energy surface for the CNCN–He van der Waals complex from which we computed rotationally resolved excitation cross-sections for energies up to 800 cm−1 using the quantum mechanical close-coupling approach. Then, hyperfine resolved transitions between the 30 low-lying pure rotational levels of CNCN were computed for temperatures ranging from 5 to 150 K using an improved infinite order sudden approach. The analysis of the scattering results showed a propensity rule in favour of Δj = ΔF1 = ΔF for the hyperfine transitions and a slight dominance of the odd Δj transitions. Using these data, we carried out non-LTE radiative transfer calculations to simulate the excitation of CNCN in molecular clouds and to constrain the physical conditions of cold dark clouds. Preliminary results showed that the abundance of CNCN derived from observational spectra has to be revisited using these new collisional data.

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Lique, François, Alexandre Zanchet, Niyazi Bulut, Javier R. Goicoechea, and Octavio Roncero. "Hyperfine excitation of SH+ by H." Astronomy & Astrophysics 638 (June 2020): A72. http://dx.doi.org/10.1051/0004-6361/202038041.

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Context. SH+ is a surprisingly widespread molecular ion in diffuse interstellar clouds. There, it plays an important role by triggering the sulfur chemistry. In addition, SH+ emission lines have been detected at the UV-illuminated edges of dense molecular clouds, so-called photo-dissociation regions (PDRs), and toward high-mass protostars. An accurate determination of the SH+ abundance and of the physical conditions prevailing in these energetic environments relies on knowing the rate coefficients of inelastic collisions between SH+ molecules and hydrogen atoms, hydrogen molecules, and electrons. Aims. We derive SH+–H fine and hyperfine-resolved rate coefficients from recent quantum calculations for the SH+–H collisions, including inelastic, exchange, and reactive processes. Methods. The method we used is based on the infinite-order sudden approach. Results. State-to-state rate coefficients between the first 31 fine levels and 61 hyperfine levels of SH+ were obtained for temperatures ranging from 10 to 1000 K. Fine-structure resolved rate coefficients present a strong propensity rule in favor of Δj = ΔN transitions. The Δj = ΔF propensity rule is observed for the hyperfine transitions. Conclusions. The new rate coefficients will help significantly in the interpretation of SH+ spectra from PDRs and UV-irradiated shocks where the abundance of hydrogen atoms with respect to hydrogen molecules can be significant.

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Rivest, R. C., M. R. Izawa, S. D. Rosner, T. J. Scholl, G. Wu, and R. A. Holt. "Laser spectroscopic measurements of hyperfine structure in Pr II." Canadian Journal of Physics 80, no. 5 (May 1, 2002): 557–62. http://dx.doi.org/10.1139/p02-009.

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We have used fast-ion-beam laser spectroscopy to measure the hyperfine structure of 36 transitions in Pr II in the wavelength range 420460 nm, obtaining the hyperfine constants of 8 odd-parity levels in the range 05079 cm1 and 32 even-parity levels in the range 22 04028 578 cm1 with a typical accuracy of 0.2%. These will find useful application in stellar elemental abundance studies. PACS Nos.: 32.30-r, 32.10-f

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Misra, Sushil K., Kingsley Mbaebie, and S. Subramanian. "Doublet separations of forbidden-hyperfine transitions in the EPR of transition-metal complexes." Journal of Physics and Chemistry of Solids 50, no. 11 (January 1989): 1157–62. http://dx.doi.org/10.1016/0022-3697(89)90025-5.

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Bouhafs, N., A. Bacmann, A. Faure, and F. Lique. "The excitation of NH2 in the interstellar medium." Monthly Notices of the Royal Astronomical Society 490, no. 2 (September 19, 2019): 2178–82. http://dx.doi.org/10.1093/mnras/stz2586.

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ABSTRACT Accurate estimation of the abundance of the NH2 radical in the interstellar medium requires accurate radiative and collisional rate coefficients. The calculation of hyperfine-resolved rate coefficients for the collisional (de-)excitation of NH2 by both ortho- and para-H2 is presented in this work. Hyperfine-resolved rate coefficients are calculated from pure rotational close-coupling rate coefficients using the Mj randomizing approximation. Rate coefficients for temperatures ranging from 5 to 150 K were computed for all hyperfine transitions among the first 15 rotational energy levels of both ortho- and para-NH2 in collisions with ortho- and para-H2. The new data were then employed in radiative transfer calculations to simulate the excitation of NH2 in typical star-forming regions such as W31C, where NH2 is seen in emission. We compared the excitation and brightness temperatures for different NH2 transitions obtained using the new and the previously available collisional data. It is found that the new rate coefficients increase the simulated line intensities by a factor ∼10–30. As a consequence, NH2 abundance derived from the observations will be significantly reduced by the use of the present rate coefficients.

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Friedreich, S., D. Barna, F. Caspers, A. Dax, R. S. Hayano, M. Hori, D. Horváth, et al. "First observation of two hyperfine transitions in antiprotonic 3He." Physics Letters B 700, no. 1 (May 2011): 1–6. http://dx.doi.org/10.1016/j.physletb.2011.04.029.

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37

Erlingsson, Sigurdur I., Yuli V. Nazarov, and Vladimir I. Fal'ko. "Hyperfine-mediated spin-flip transitions in GaAs quantum dots." Physica E: Low-dimensional Systems and Nanostructures 12, no. 1-4 (January 2002): 823–26. http://dx.doi.org/10.1016/s1386-9477(01)00446-5.

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Kalvans, L., and L. Kalvāns. "Saturation Effects of Dark Magneto-Optical Resonances Observed on the Alkali D1 Line." Latvian Journal of Physics and Technical Sciences 47, no. 2 (January 1, 2010): 38–48. http://dx.doi.org/10.2478/v10047-010-0006-1.

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Saturation Effects of Dark Magneto-Optical Resonances Observed on the AlkaliD1LineTheoretical studies of saturation effects of dark magneto-optical resonances are presented. A model based on the optical Bloch equations is applied to simulate numerically the alkaliD1excitation in external magnetic field. The laser power densities at which the expected dark resonance contrast reaches maximum are analyzed and correlated with the quantum superposition states induced by exciting laser field. Fictional hyperfine structure constants for the excited state are used to vary the selection efficiency of hyperfine transitions.

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39

Lara-Moreno, Miguel, Thierry Stoecklin, and Philippe Halvick. "Resolved fine and hyperfine state-to-state rate coefficients for the rotational transitions of C3N induced by collision with He." Monthly Notices of the Royal Astronomical Society 507, no. 3 (September 2, 2021): 4086–94. http://dx.doi.org/10.1093/mnras/stab2453.

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ABSTRACT The fine and hyperfine resolved state-to-state rate coefficients for the rotational (de)excitation of C3N by collision with helium are computed. To this aim a 2D potential energy surface is calculated for this system. The recoupling method is used to obtain the fine and hyperfine structure resolved rate coefficients from spin-free close-coupling calculations. These results are compared with those given by the infinite-order sudden approximation and the M-randomizing limit. General propensity rules for the transitions are also found and analysed.

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40

Levshakov, S. A., I. I. Agafonova, C. Henkel, Kee-Tae Kim, M. G. Kozlov, B. Lankhaar, and W. Yang. "Probing the electron-to-proton mass ratio gradient in the Milky Way with Class I methanol masers." Monthly Notices of the Royal Astronomical Society 511, no. 1 (January 11, 2022): 413–24. http://dx.doi.org/10.1093/mnras/stac024.

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ABSTRACT We estimate limits on non-universal coupling of hypothetical hidden fields to standard matter by evaluating the fractional changes in the electron-to-proton mass ratio, μ = me/mp, based on observations of Class I methanol masers distributed in the Milky Way disc over the range of the Galactocentric distances $4 \lesssim R \lesssim 12$ kpc. The velocity offsets ΔV = V44 − V95 measured between the 44- and 95-GHz methanol lines provide, so far, one of the most stringent constraints on the spatial gradient kμ ≡ d(Δμ/μ)/dR < 2 × 10−9 kpc−1 and the upper limit on Δμ/μ <2 × 10−8, where Δμ/μ = $(\mu _{\rm \scriptscriptstyle obs}-\mu _{\rm \scriptscriptstyle lab})/\mu _{\rm \scriptscriptstyle lab}$. We also find that the offsets ΔV are clustered into two groups which are separated by $\delta _{\scriptscriptstyle \Delta V} = 0.022 \pm 0.003$ km s−1 (1σ confidence level). The grouping is most probably due to the dominance of different hyperfine transitions in the 44- and 95-GHz methanol maser emission. Which transition becomes favoured is determined by an alignment (polarization) of the nuclear spins of the four hydrogen atoms in the methanol molecule. This result confirms that there are preferred hyperfine transitions involved in the methanol maser action.

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Kłos, J., P. J. Dagdigian, M. H. Alexander, A. Faure, and F. Lique. "The excitation of OH by H2 revisited – II. Hyperfine resolved rate coefficients." Monthly Notices of the Royal Astronomical Society 493, no. 3 (February 24, 2020): 3491–95. http://dx.doi.org/10.1093/mnras/staa530.

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ABSTRACT Observations of hyperfine resolved transitions of the hydroxyl radical (OH) are unique probes of the physical conditions in molecular clouds. In particular, hyperfine intensities can be used as an effective thermometer over a wide range of molecular densities. Accurate modelling of the OH emission spectra requires the calculation of collisional rate coefficients for the excitation of OH by H2, the most abundant collisional partner in the molecular clouds. Here, we determine hyperfine resolved rate coefficients for the excitation of OH by H2 using a recently developed highly accurate potential energy surface. State-to-state rate coefficients between the lower hyperfine levels were calculated using recoupling techniques for temperature ranging from 10 to 150 K. Significant differences were found with the earlier values currently used in astrophysical models, the new rate coefficients being larger than the previous ones. Finally, we compute the excitation of the OH radical in cold molecular clouds and star-forming regions. The new rate coefficients were found to increase the hyperfine intensities by a factor of ∼1–2. Consequently, we recommend using this new set of data in any astrophysical model of OH excitation.

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Bakalov, Dimitar, and Mihail Stoilov. "Toward the measurement of the hyperfine structure of muonic hydrogen in the FAMU experiment: Multi-pass cavity optimization for experiments with pulsed sources." EPJ Web of Conferences 181 (2018): 01033. http://dx.doi.org/10.1051/epjconf/201818101033.

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We consider a simplified model of the optical multi-pass cavity that is being currently developed by the FAMU collaboration for the measurement of the hyperfine splitting in the ground state of muonic hydrogen and of the Zemach radius of the proton. The model is focused on the time distribution of the events of laser-stimulated hyperfine transitions in the muonuc atom and may be helpful in the preliminary design of the FAMU experimental set-up and, more generally, in the optimization of multi-pass optical cavities for experiments with pulsed lasers.

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Li, Tang, and Xiaowei Zhang. "The Prime Beat Components Extraction Method for the Time Spectra Analysis of Nuclear Resonant Forward Scattering." Materials 12, no. 10 (May 21, 2019): 1657. http://dx.doi.org/10.3390/ma12101657.

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Spectra of quantum beats (QBs) of nuclear resonant forward scattering contain the interference information of all allowed energy transitions of a nucleus, which makes it complicated to extract hyperfine structure directly. Here, we propose a new method, based upon the extraction of prime beat components, to understand QBs. In this method, the origin of major spectral lines in the Fourier Transformation of QBs is studied, and the energy levels of hyperfine structure are obtained directly from the QBs. We applied this method to the temperature dependent QBs of hematite. The Morin temperature and hyperfine structure obtained by this method are in consistent with that by conventional Mössbauer spectroscopy (MS). It serves to interpret the components of QBs of nuclear resonant forward scattering as simple as the conventional (MS).

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Chefai, A., N. E. Jaidane, K. Hammami, and F. Lique. "Fine and hyperfine excitation of CCN by He." Monthly Notices of the Royal Astronomical Society 497, no. 2 (July 13, 2020): 1862–69. http://dx.doi.org/10.1093/mnras/staa2058.

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ABSTRACT The relative abundance of cyanide and isocyanide molecules is a sensitive tracer of the physical conditions in the interstellar and circumstellar media. Accurate modelling of collisional and radiative processes implying these species opens the way for accurate estimation of their abundances. The present paper focuses on the computation of collisional rate coefficients for fine and hyperfine (de-)excitation of the CCN molecule (one of the C2N isomers) in collision with He, for temperatures up to 150 K. Using a time independent coupled-channel approach, scattering calculations were performed for transitions implying the lowest 56 fine structure levels and the corresponding 166 hyperfine structure levels belonging to both 2Π1/2 and 2Π3/2 spin-orbit manifolds. We provided, for the first time, realistic collisional data for the CCN radical. Propensity rules for fine and hyperfine transitions are discussed. As a first application, we evaluated the impact of these new data on the astrophysical modelling through radiative transfer calculations. We obtained the brightness and excitation temperatures of selected lines observed towards circumstellar envelopes and we found that local thermodynamic equilibrium conditions are not fulfilled for this species. As a consequence, our results indicate that the abundance of the CCN derived from the observations has to be revised since the observation modelling strongly depends on the collisional data used.

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Masterman, D., S. D. Rosner, T. J. Scholl, A. Sharikova, and R. A. Holt. "Isotope shifts and hyperfine structure in Sm II." Canadian Journal of Physics 81, no. 12 (December 1, 2003): 1389–401. http://dx.doi.org/10.1139/p03-106.

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We have measured the isotope shifts of 87 transitions in Sm II in the 418465 nm spectral region and the magnetic-dipole and electric-quadrupole hyperfine constants of 13 low-lying even-parity metastable levels and 76 odd-parity levels. These results will be immediately applicable to stellar spectroscopy.PACS Nos.: 32.30.r, 32.10.f

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Zhu, Chengcheng, Hailing Wang, Ben Chen, Yini Chen, Tao Yang, Jianping Yin, and Jinjun Liu. "Fine and hyperfine interactions of PbF studied by laser-induced fluorescence spectroscopy." Journal of Chemical Physics 157, no. 8 (August 28, 2022): 084307. http://dx.doi.org/10.1063/5.0099716.

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The fine and hyperfine interactions in PbF have been studied using the laser-induced fluorescence (LIF) spectroscopy method. Cold PbF molecular beam was produced by laser-ablating a Pb rod under jet-cooled conditions, followed by the reaction with SF6. The LIF excitation spectrum of the (0, 0) band in the B2Σ+– X2Π1/2 system of the 208PbF, 207PbF, and 206PbF isotopologues has been recorded with rotational, fine structure, and hyperfine-structure resolution. Transitions in the LIF spectrum were assigned and combined with the previous X2Π3/2– X2Π1/2 emission spectrum in the near-infrared region [Ziebarth et al., J. Mol. Spectrosc. 191, 108–116 (1998)] and the X2Π1/2 state pure rotational spectrum of PbF [Mawhorter et al., Phys. Rev. A 84, 022508 (2011)] in a global fit to derive the rotational, spin–orbit, spin–rotation, and hyperfine interaction parameters of the ground ( X2Π1/2) and the excited ( B2Σ+) electronic states. Molecular constants determined in the present work are compared with previously reported values. Particularly, the significance of the hyperfine parameters, A⊥ and A‖, of 207Pb is discussed.

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47

Elbel, M., and R. Quad. "The Quadrupole Moments of the Stable Nuclei of Sulphur and Chlorine." Zeitschrift für Naturforschung A 41, no. 1-2 (February 1, 1986): 15–18. http://dx.doi.org/10.1515/zna-1986-1-205.

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By means of collinear laser spectroscopy the hyperfine structure of two transitions in the ionic spectra of sulphur and chlorine has been measured. The hyperfine constants of the involved levels have been determined. From them and by means of the spin-orbit coupling constants of the involved p-electrons the quadrupole moments of 33S, 35Cl and 37Cl could be determined anew. The importance of the new values is seen in the fact that in the case of sulphur they result from measurements at the free ion or, in the case of chlorine, that they result from an electron other than 3 p.

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48

Krause, H., and D. H. Sutter. "The 14N Nuclear Quadrupole Coupling in E- and Z-C-Cyanomethanimine; its Prediction from Restricted Hartree-Fock Wave Functions and its Experimental Determination by High Resolution Microwave Spectroscopy." Zeitschrift für Naturforschung A 47, no. 4 (April 1, 1992): 573–82. http://dx.doi.org/10.1515/zna-1992-0405.

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AbstractThe 14N hyperfine multiplets of low-7 rotational transitions of the E and Z isomers of HN = CH - C ≡ N, produced by flash pyrolysis from (CH3)2N -C ≡ N as precursor, were observed and analysed. The quadrupole coupling constants determined are (c-axis perpendicular to the molecular plane): The observed hfs multiplets were predicted with reasonable accuracy from RHF/6-311G** field gradients, once the latter had been scaled appropriately to compensate partly for the typical errors in the RHF-wave functions. The hitherto unmeasured 14N hyperfine multiplets of the related pyruvonitriles, H - N = C(CH3) - C ≡ N, are predicted.

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Fujitake, Masaharu, and Eizi Hirota. "The microwave spectrum of the ClS2 free radical." Canadian Journal of Physics 72, no. 11-12 (November 1, 1994): 1043–50. http://dx.doi.org/10.1139/p94-136.

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The rotational spectrum of the ClS2 free radical in the gaseous phase has been observed in the millimetre- and submillimetre-wave regions. The ClS2 radical was generated by a dc glow discharge in either S2Cl2 or SCl2. Both a- and b-type R-branch transitions, most of which were split into two fine structure components, were detected for both of the 35Cl and 37Cl isotopic species in the ground vibronic state. As expected from the small hyperfine interaction constants reported by an electron spin resonance (ESR) study, the hyperfine structure was resolved for none of the transitions observed in the present study. Analysis of the observed transition frequencies yielded rotational and centrifugal distortion constants and also spin–rotation interaction constants with their centrifugal corrections. The spin–rotation interaction constants obtained in the present study were consistent with g values of the ESR study. The rotational constants of the two isotopic species led to the structure parameters r(S—S) = 1.906 (7) Å, r(S—Cl) = 2.071 (5) Å, and θ(SSCl) = 110.3 (4)°. A harmonic force field was derived from the observed centrifugal distortion constants and inertial defects combined with the ν1 frequency reported in literature on electronic spectroscopy. This harmonic force field yielded the ν2 and ν3 frequencies (445 (21) and 213.0 (2) cm−1, respectively, for 35ClS2), which differed considerably from the values reported previously.

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Rosner, S. D., and R. A. Holt. "Hyperfine structure and isotope shifts in Mo II." Canadian Journal of Physics 94, no. 11 (November 2016): 1195–99. http://dx.doi.org/10.1139/cjp-2016-0192.

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We have applied fast-ion-beam laser-fluorescence spectroscopy to measure the hyperfine structures of seven even-parity and six odd-parity levels in Mo II and the isotope shifts of nine transitions in the wavelength range 424.5–443.4 nm. These are the first measurements of these parameters and almost the first such measurements in Mo II. These atomic data are essential for astrophysical studies of chemical abundances, allowing correction for saturation and the effects of blended lines. They also provide important constraints on stellar diffusion modeling, particularly in chemically peculiar (CP) stars, and serve as valuable input to semi-empirical theoretical models of hyperfine structure and isotope shifts.

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