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Journal articles on the topic 'Photoionization'

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Author: Grafiati

Published: 4 June 2021

Last updated: 31 July 2024

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1

Zhao, Yujie, Pei Huang, Li Li, Yousheng Zhan, Ke Wang, Haohang Yang, Jianhui Jin, et al. "Vacuum ultraviolet photoionization and dissociative photoionization of toluene: Experimental and theoretical insights." European Journal of Mass Spectrometry 27, no. 5 (October 2021): 166–80. http://dx.doi.org/10.1177/14690667211042707.

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The photoionization and dissociative photoionization of toluene have been studied using synchrotron radiation vacuum ultraviolet light with photon energy in the range of 8.50–25.50 eV. The ionization energies (8.82 eV) and double ionization energies (23.80 eV) of toluene as well as the appearance energies for its major fragments C7H7+ (11.17/10.71 eV), C6H5+ (13.73 eV), C5H6+ (13.58/12.50 eV), C5H5+ (16.23 eV), C4H5+ (15.64 eV), C4H4+ (16.10 eV) and C4H3+ (17.11 eV) are determined, respectively by using photoionization efficiency spectrometry. With the help of experimental and theoretical results, seven dissociative photoionization channels have been proposed: C7H7+ + H, C6H5+ + CH3, C5H6+ + C2H2, C5H5+ + C2H2 + H, C4H5+ + C3H3, C4H4+ + C3H4 and C4H3+ + C3H4 + H. In addition, the geometries of the intermediates, transition states and products involved in these photoionization and dissociative photoionization processes have been performed at the B3LYP/6-311++G(d, p) level. The mechanisms of dissociative photoionization of toluene and the intermediates and transition states involved are discussed in detail. Generally speaking, the experimental results are in agreement with theoretical calculations in this work and published literature results. Especially the mechanisms of dissociative photoionization to C4H5+, C4H4+ and C4H3+ were discussed for the first time in this work. This investigation may provide useful information on understanding the photoionization and dissociative photoionization of toluene.

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2

Singor, Adam, Liam H. Scarlett, Mark C. Zammit, Igor Bray, and Dmitry V. Fursa. "Photoionization from the Ground and Excited Vibrational States of H2+ and Its Deuterated Isotopologues." Astrophysical Journal Supplement Series 269, no. 1 (November 1, 2023): 19. http://dx.doi.org/10.3847/1538-4365/acf840.

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Abstract Photoionization cross sections and rate coefficients have been calculated for all bound vibrational levels of the 1sσ g state of H 2 + , HD+, and D 2 + . The Born–Oppenheimer approximation is employed in our calculation of vibrationally resolved photoionization cross sections. Vibrationally resolved and local thermal equilibrium photoionization rate coefficients are presented for photon temperatures less than 50,000 K and are found to be several orders of magnitude larger than previous results in the literature. Analytic fits for the vibrationally resolved and local thermal equilibrium photoionization rate coefficients are provided. Near-threshold oscillations in the vibrationally resolved photoionization are observed. A benchmark set of photoionization cross sections are presented. Fixed-nuclei photoionization cross sections are calculated using two-center true continuum wave functions and are verified by comparison with previous calculations and are found to be in excellent agreement in all cases. Data files for our set of benchmark cross sections, rate coefficients, and fitting parameters for H 2 + , HD+, and D 2 + are available on Zenodo under an open-source Creative Commons Attribution license at doi:10.5281/zenodo.8304061.

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3

Harrington, J. Patrick. "Photoionization Models." Symposium - International Astronomical Union 131 (1989): 157–66. http://dx.doi.org/10.1017/s0074180900137738.

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A recent comparison of the photoionization models generated by five independent codes run with the same density and stellar radiation shows substantial agreement. Problems are more likely to arise with the defining parameters: the density distribution should be based on observed images, and the ionizing radiation should be from model atmosphere calculations, which, however, are inadequate for stars with winds. Models can be improved by including dust and by incorporating, self-consistently, radiative transfer in optically thick lines. Future work may extend modeling to axially-symmetric objects, to the interface with the hot, shocked, stellar wind, and to the molecular component present around many nebulae.

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4

Bordas, C., F. L�pine, C. Nicole, and M. J. J. Vrakking. "Photoionization Microscopy." Physica Scripta 110 (2004): 68. http://dx.doi.org/10.1238/physica.topical.110a00068.

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5

Gorczyca, T. W., T.-G. Lee, and M. S. Pindzola. "Photoionization-Excitation and Double Photoionization of He@C60." Journal of Physics: Conference Series 488, no. 2 (April 10, 2014): 022038. http://dx.doi.org/10.1088/1742-6596/488/2/022038.

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6

LeFevre, H. J., R. P. Drake, and C. C. Kuranz. "The evolution of curvature in planar, photoionization-driven heat fronts." Physics of Plasmas 29, no. 8 (August 2022): 084501. http://dx.doi.org/10.1063/5.0088624.

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Photoionized plasmas are common in astrophysics and cosmology, especially in space near compact objects, and there are effects from photoionization in high-energy-density plasmas due to the large radiation fields present. Photoionized plasmas are an active area of laboratory research and there are currently experiments to study photoionization-supported heat fronts. These photoionization fronts differ from the physics of diffusive radiation waves, commonly called Marshak waves, that are also an active area of research. This work uses a geometric argument to describe the expected evolution of the photoionization front curvature, in a planar geometry. It then compares this curvature to that of a Marshak wave as a method of diagnosing a heat front experiment. It is found that while the curvature of a planar Marshak wave increases in time, it decreases for a photoionization front. A comparison of radiation energy and electron heat fluxes through the container for the heat front propagating medium demonstrates that the geometric argument for the photoionization front curvature is sufficient. This comparison also demonstrates that wall losses are not significant in a photoionization front because the post-front region is very optically thin. A discussion of the implication this work has on material choice in the targets for an experiment follows.

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7

D’yachkov A.B., Gorkunov A. A., Labozin A. V., Mironov S. M., Firsov V. A., Tsvetkov G. O., and Panchenko V. Ya. "Effect of Laser Polarization on Photoionization Efficiency of Lutetium." Optics and Spectroscopy 130, no. 12 (2022): 1525. http://dx.doi.org/10.21883/eos.2022.12.55237.3034-22.

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The effect of laser radiation polarization on the photoionization of lutetium is studied using three-stage scheme 5d6s2 2D3/2-5d6s6p 4Fo5/2-5d6s7s 4D3/2- (53375 cm-1)o1/2. It is shown that in a number of cases, there is a limitation of photoionization associated with the features of coherent photoexcitation. Keywords: laser selective photoionization, lutetium-177.

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8

Popova, Maria M., Maksim D. Kiselev, Sergei M. Burkov, Elena V. Gryzlova, and Alexei N. Grum-Grzhimailo. "Spectroscopic Peculiarities at Ionization of Excited 2p5(2PJf)3s[K]0,1,2 States of Ne: Cooper Minima and Autoionizing Resonances." Atoms 10, no. 4 (September 26, 2022): 102. http://dx.doi.org/10.3390/atoms10040102.

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An extensive study of photoionization from neon excited states was performed. The R-matrix approach was applied to calculate a photoionization cross-section from the metastable 2p5(2PJf)3s[K]0,2 and dipole-allowed 2p5(2PJf)3s[K]1 states. The resonance structures and Cooper minimum accessible in photoionization from the excited states by the photons with energy below 30 eV were analyzed. The parameters of the lowest autoionizing states (AISs) of even parity were extracted by fitting of the photoionization cross-section. For the dipole-allowed states, calculations are presented for unpolarized, linearly and circularly polarized radiation.

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9

Wang, De-Hua, Xin-Yue Sun, and Tong Shi. "Photoionization microscopy of the Rydberg Rb atom under a continuous infrared radiation laser field." Canadian Journal of Chemistry 98, no. 1 (January 2020): 24–33. http://dx.doi.org/10.1139/cjc-2019-0267.

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The photoionization microscopy of the Rydberg Rb atom exposed to a continuous infrared radiation laser field is investigated based on the semiclassical open orbit theory. In contrast to the photoionization of the Rydberg hydrogen atom, the ionic core-scattering effect plays an important role in the photoionization of the Rb atom. Due to the core-scattering effect and the laser field, the electron trajectories become chaotic. A huge number of ionization trajectories from the ionic source to the detector plane appear, which makes the oscillatory pattern in the electron probability distribution become much more complicated. The ρ–θ curve on the detector plane exhibits a self-similar fractal structure for the ionization trajectories of the Rydberg Rb atom in the laser field. Due to constructive and destructive quantum interference of different electron trajectories, a series of concentric rings appear in the photoionization microscopy interference patterns on the detector plane. The electron probability density distributions on the detector are found to be changed sensitively with the scaled electron energy and the laser wavelength. Even as the detector plane is located at a macroscopic distance from the photoionization source, the photoionization microscopy interference patterns can be observed clearly. These calculations may provide a valuable contribution to the actual experimental study of the photoionization microscopy of non-hydrogenic Rydberg atom in the laser field.

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10

Masuoka, Toshio. "Single, double, and triple photoionization of molecules using synchrotron radiation." Canadian Journal of Physics 74, no. 11-12 (November 1, 1996): 850–55. http://dx.doi.org/10.1139/p96-121.

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The recent advances concerning production and dissociation dynamics of multiply-charged molecules using synchrotron radiation are discussed with emphasis on dissociative double photoionization in the valence region. In the determination of the ratio of double to single photoionization, both molecular and dissociative processes are properly included. Kinetic-energy release and anisotropic fragmentation in dissociative double photoionization of carbon monoxide are also discussed.

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11

Kučas, Sigitas, Aušra Kynienė, Šarūnas Masys, and Valdas Jonauskas. "Multiple photoionization cross sections for Fe2+ K shell." Astronomy & Astrophysics 643 (October 29, 2020): A46. http://dx.doi.org/10.1051/0004-6361/202038762.

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Multiple photoionization cross sections from the K shell are studied for all levels of the Fe2+ 3d6 configuration. The study shows that the quadruple photoionization leads to the largest cross sections. A large variation in the multiple photoionization cross sections is determined among the levels of the Fe2+ 3d6 configuration. Main decay branches of radiative and Auger cascades, following the photoionization of the K shell for the ground configuration of the Fe2+ ion, are identified. The radiative and Auger cascade is studied by considering transitions among energy levels and subconfigurations. The obtained data for ion yields are compared with previous calculations produced for configuration averages.

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12

Izmailov A. Ch. "Sub-Doppler resonances caused by photoionization of atoms in thin gas cells." Optics and Spectroscopy 132, no. 3 (2022): 346. http://dx.doi.org/10.21883/eos.2022.03.53555.2785-21.

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By analogy with the well-tested method of high-resolution spectroscopy in thin gas cells for the processes of optical pumping of atoms, this work shows the possibility of detecting narrow sub-Doppler optical resonances caused directly by straight photoionization of atoms (or molecules) in such cells. The structure of the established nontrivial resonances substantially depends on the probability of photoionization of atoms and dimensions of such a cell, the internal thickness of which is many times smaller than its diameter. Of particular interest is the broadening of the considered sub-Doppler resonances, which is determined directly by the photoionization cross section of atoms and the intensity of radiation causing ionization. Under certain conditions, such photoionization broadening can be measured experimentally with high accuracy, as a result of which it is possible to obtain new important information about ionization processes in atoms and molecules. Keywords: sub-Doppler resonances, photoionization of atoms, thin gas cell, transit-time relaxation of atoms.

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13

Fischer, Ingo, Thomas Schüßler, Hans-Jürgen Deyerl, Mohamed Elhanine, and Christian Alcaraz. "Photoionization and dissociative photoionization of the allyl radical, C3H5." International Journal of Mass Spectrometry 261, no. 2-3 (March 2007): 227–33. http://dx.doi.org/10.1016/j.ijms.2006.09.023.

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14

Zhao, Yu-jie, You-sheng Zhan, Li Li, Xin Li, Xiang-yu Lian, Pei Huang, Liu-si Sheng, and Jun Chen. "Theoretical Investigation on Photoionization and Dissociative Photoionization of Toluene." Chinese Journal of Chemical Physics 30, no. 3 (June 27, 2017): 303–11. http://dx.doi.org/10.1063/1674-0068/30/cjcp1703044.

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15

Hillier, D. John. "Photoionization and Electron–Ion Recombination in Astrophysical Plasmas." Atoms 11, no. 3 (March 9, 2023): 54. http://dx.doi.org/10.3390/atoms11030054.

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Photoionization and its inverse, electron–ion recombination, are key processes that influence many astrophysical plasmas (and gasses), and the diagnostics that we use to analyze the plasmas. In this review we provide a brief overview of the importance of photoionization and recombination in astrophysics. We highlight how the data needed for spectral analyses, and the required accuracy, varies considerably in different astrophysical environments. We then discuss photoionization processes, highlighting resonances in their cross-sections. Next we discuss radiative recombination, and low and high temperature dielectronic recombination. The possible suppression of low temperature dielectronic recombination (LTDR) and high temperature dielectronic recombination (HTDR) due to the radiation field and high densities is discussed. Finally we discuss a few astrophysical examples to highlight photoionization and recombination processes.

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16

Sheng, Liusi, Fei Qi, Hui Gao, Yunwu Zhang, Shuqin Yu, and Wai-Kee Li. "Experimental and theoretical study of the photoionization and dissociative photoionizations of dichlorodifluoromethane." International Journal of Mass Spectrometry and Ion Processes 161, no. 1-3 (February 1997): 151–59. http://dx.doi.org/10.1016/s0168-1176(96)04506-5.

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17

Zatsarinny, Oleg, and Swaraj Tayal. "Partial Photoionization Cross Sections of Chromium from the Ground and Excited States." Atoms 8, no. 3 (August 27, 2020): 51. http://dx.doi.org/10.3390/atoms8030051.

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Partial and total photoionization cross sections of iron-peak elements are important for the determination of abundances in late-type stars and nebular objects. We have investigated photoionization of neutral chromium from the ground and excited states in the low energy region from the first ionization threshold at 6.77 eV to 30 eV. Accurate descriptions of the initial bound states of Cr I and the final residual Cr II ionic states have been obtained in the multiconfiguration Hartree-Fock method together with adjustable configuration expansions and term-dependent non-orthogonal orbitals. The B-spline R-matrix method has been used for the calculation of photoionization cross sections. The 194 LS final ionic states of Cr II 3d44s, 3d34s2, 3d5, 3d44p, and 3d34s4p principal configurations have been included in the close-coupling expansion. The inclusion of all terms of these configurations has significant impact on the near-threshold resonance structures as well as on the nonresonant background cross sections. Total photoionization cross sections from the ground 3d54sa7S and excited 3d54sa5S, 3d44s2a5D, 3d54pz5P, and 3d44s4py5P states of Cr I have been compared with other available R-matrix calculation to estimate the likely uncertainties in photoionization cross sections. We analyzed the partial photoionization cross sections for leaving the residual ion in various states to identify the important scattering channels, and noted that 3d electron ionization channel becomes dominant at higher energies.

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18

Pradhan, Anil. "Photoionization and Opacity." Atoms 11, no. 3 (March 6, 2023): 52. http://dx.doi.org/10.3390/atoms11030052.

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Opacity determines radiation transport through material media. In a plasma source, the primary contributors to atomic opacity are bound–bound line transitions and bound-free photoionization into the continuum. We review the theoretical methodology for state-of-the-art photoionization calculations based on the R-matrix method as employed in the Opacity Project, the Iron Project, and solution of the heretofore unsolved problem of plasma broadening of autoionizing resonances due to electron impact, Stark (electric microfields), Doppler (thermal), and core-excitations. R-matrix opacity calculations entail huge amount of atomic data and calculations of unprecedented complexity. It is shown that in high-energy-density (HED) plasmas, photoionization cross sections become 3-D energy–temperature–density-dependent owing to considerable attenuation of autoionizing resonance profiles. Hence, differential oscillator strengths and monochromatic opacities are redistributed in energy. Consequently, Rosseland and Planck mean opacities are affected significantly.

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19

Kučas, Sigitas, Aušra Kynienė, Šarūnas Masys, and Valdas Jonauskas. "Multiple photoionization for the 2s subshell in the iron atom." Monthly Notices of the Royal Astronomical Society 516, no. 3 (September 9, 2022): 3113–19. http://dx.doi.org/10.1093/mnras/stac2461.

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ABSTRACT Multiple photoionization is analysed as a result of radiative and Auger cascade following ionization by photon from the 2s subshell. The study includes 34 levels of the 3d64s2 configuration of the Fe atom. The multiple-photoionization cross-sections from the levels of the ground configuration to the generated ions and their configurations are analysed. This study demonstrates that the photoionization of the 2s subshell produces mainly states of the Fe5+ ion. The highest charge state produced by the photoionization equals Fe6+. The difference of the ion yields from the investigated levels of the iron atom reaches ∼ 4% for the Fe 5+ and Fe6+ ions. Main branches of the cascade decay are identified in the study. It is determined that the two strongest branches of the cascade lead to states of the Fe5+ ion.

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20

Baig, Muhammad Aslam. "Measurement of Photoionization Cross-Section for the Excited States of Atoms: A Review." Atoms 10, no. 2 (April 14, 2022): 39. http://dx.doi.org/10.3390/atoms10020039.

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A review of experimental studies of the measurement of the photoionization cross-section for the excited states of the alkali atoms, alkaline earth atoms, and rare-gas atoms is presented, with emphasis on using multi-step laser excitation, ionization, and the saturation technique. The dependence of the photoionization cross-section from different intermediate states populated in the first step and ionized in the second step are discussed, including results on the photoionization cross-sections measured above the first ionization threshold. Results based on different polarizations of the exciting and the ionizing dye lasers are also discussed. Examples are provided, illustrating the photoionization cross-sections measured using thermionic diode ion detector, atomic beam apparatus in conjunction with a time-of-flight mass spectrometer and DC/RF glow discharge cell as an optogalvanic detection.

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21

Schippers, Stefan, and Alfred Müller. "Photoionization of Astrophysically Relevant Atomic Ions at PIPE." Atoms 8, no. 3 (August 18, 2020): 45. http://dx.doi.org/10.3390/atoms8030045.

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We review recent work on the photoionization of atomic ions of astrophysical interest that has been carried out at the photon-ion merged-beams setup PIPE, a permanently installed end station at the XUV beamline P04 of the PETRA III synchrotron radiation source operated by DESY in Hamburg, Germany. Our results on single and multiple L-shell photoionization of Fe+, Fe2+, and Fe3+ ions, and on single and multiple K-shell photoionization of C−, C+, C4+, Ne+, and Si2+ ions are discussed in astrophysical contexts. Moreover, these experimental results bear witness of the fact that the implementation of the photon-ion merged-beams method at one of the world’s brightest synchrotron light sources has led to a breakthrough for the experimental study of atomic inner-shell photoionization processes with ions.

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22

Singor, Adam, Dmitry Fursa, Igor Bray, and Robert McEachran. "A Fully Relativistic Approach to Photon Scattering and Photoionization of Alkali Atoms." Atoms 9, no. 3 (July 8, 2021): 42. http://dx.doi.org/10.3390/atoms9030042.

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A fully relativistic approach to calculating photoionization and photon-atom scattering cross sections for quasi one-electron atoms is presented. An extensive set of photoionization cross sections have been calculated for alkali atoms: lithium, sodium, potassium, rubidium and cesium. The importance of relativistic effects and core polarization on the depth and position of the Cooper minimum in the photoionization cross section is investigated. Good agreement was found with previous Dirac-based B-spline R-matrix calculations of Zatsarinny and Tayal and recent experimental results.

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23

Hochlaf, M., H. Kjeldsen, F. Penent, R. I. Hall, P. Lablanquie, M. Lavollée, and J. H. D. Eland. "Two spectrometers for threshold photoelectron coincidence studies of double photoionization." Canadian Journal of Physics 74, no. 11-12 (November 1, 1996): 856–60. http://dx.doi.org/10.1139/p96-800.

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We present here two simple instruments for the study of double photoionization processes at threshold. They rely on the coincidence measurement of two near-zero energy electrons, which are collected by a penetrating field technique, and energy selected either by time-of-flight analysis (1st setup) or by electrostatic filtering in a hemispherical analyzer (2nd setup). Performance of the apparatus is demonstrated on Ar threshold double photoionization, and used to show the importance of two step double photoionization routes at Ar and Kr double ionization threshold.

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24

D’yachkov A. B., Mironov S. M., and Tsvetkov G. O. "Coherent kinetics of a multistage λ scheme for laser isotope separation." Optics and Spectroscopy 130, no. 9 (2022): 1092. http://dx.doi.org/10.21883/eos.2022.09.54824.3036-22.

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Analytical solutions of the Schr?dinger equations for coherent excitation of an atom in the scheme of two- and three-stage photoionization are obtained as applied to the problem of laser isotope separation. A feature of the study is the introduction of laser excitation from an additional initial state to increase the fraction of the atoms involved in the separation process. The optimal from the points of view of photoion ratios of radiation intensities at individual photoionization stages are found. Key words: laser photoionization, laser isotope separation.

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25

Li, Yanbo, Weiye Chen, Long Zhu, Huanhuan Wang, Jiwen Guan, Xiaobin Shan, Fuyi Liu, and Zhandong Wang. "Intramolecular CH3-migration-controlled cation reactions in the VUV photochemistry of 2-methyl-3-buten-2-ol investigated by synchrotron photoionization mass spectrometry and theoretical calculations." Physical Chemistry Chemical Physics 23, no. 17 (2021): 10456–67. http://dx.doi.org/10.1039/d1cp00490e.

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CH₃ migration-controlled fragmentations via conventional TS and roaming pathways are reported in the dissociative photoionization of 2-methyl-3-buten-2-ol, which are examined by synchrotron photoionization spectroscopy and theoretical calculations.

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26

Oketch, F., and H. Oyoko. "A theoretical study of variation of photoionization cross section of donor impurities in a GaAs quantum dot of cylindrical geometry with incident photon frequency, donor location along the dot axis and applied uniaxial stress." Revista Mexicana de Física 66, no. 1 (December 28, 2019): 35. http://dx.doi.org/10.31349/revmexfis.66.35.

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In this work, we have used a variational technique within the effective mass approximation to study the variation of the photoionization cross section of a donor impurity in a cylindrical GaAs quantum dot with incident photon frequencies and applied uniaxial stress. We have used the dipole approximation and assumed that the barrier potential is infinite. Our results show that the photoionization cross section begins at a finite value and increases with increasing frequency until it reaches a peak and then it decreases gradually, almost exponentially, until it reaches a finite value when it is almost insensitive to any further increase in frequency. Furthermore, for a particular quantum dot length, the photoionization cross section decreases with increasing applied uniaxial stress. We have also noted that the longer the quantum well dot the larger is the photoionization cross section

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27

Moccia, Roberto, and Pietro Spizzo. "A GTO basis set calculation of properties of the continuum. Photoionization and resonances of He." Canadian Journal of Chemistry 70, no. 2 (February 1, 1992): 513–19. http://dx.doi.org/10.1139/v92-073.

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By using the K-matrix technique for the continuum states that was previously employed with particularly diffuse L2 basis sets, it is shown that GTO bases are also capable of yielding accurate values for the properties belonging to the electronic continuum. The method has been tested for helium and proved of satisfactory accuracy also for the analysis of the autoionizing states. The results include the phase shifts of the continuum states of the 1Seand 1P° manifolds, the properties of the lowest resonances of these symmetries, the ground state photoionization cross section, and the S contribution to the 1s2p1P° photoionization cross section. The results obtained suggest that the proposed technique should be useful for computing molecular differential photoionization cross sections by exploiting the widely used codes that employ GTO bases. Keywords: photoionization, Gaussian basis sets, helium, autoionizing states.

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28

Dourneuf, M. Le, S. N. Nahar, and A. K. Pradhan. "Photoionization of Fe+." Journal of Physics B: Atomic, Molecular and Optical Physics 26, no. 1 (January 14, 1993): L1—L6. http://dx.doi.org/10.1088/0953-4075/26/1/001.

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29

Lévesque, S., J.-M. Gagné, and F. Babin. "Optogalvanic photoionization spectroscopy." Journal of Physics B: Atomic, Molecular and Optical Physics 30, no. 16 (August 28, 1997): 3744. http://dx.doi.org/10.1088/0953-4075/30/16/013.

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30

Lévesque, S., J.-M. Gagné, and F. Babin. "Optogalvanic photoionization spectroscopy." Journal of Physics B: Atomic, Molecular and Optical Physics 30, no. 5 (March 14, 1997): 1331–46. http://dx.doi.org/10.1088/0953-4075/30/5/024.

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31

Helm, Hanspeter, and Philip C. Cosby. "Photoionization ofN2EΣg+3." Physical Review A 38, no. 1 (July 1, 1988): 115–25. http://dx.doi.org/10.1103/physreva.38.115.

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32

Coelho Rezende, Gustavo, Stéphane Le Calvé, Jürgen J. Brandner, and David Newport. "Micro photoionization detectors." Sensors and Actuators B: Chemical 287 (May 2019): 86–94. http://dx.doi.org/10.1016/j.snb.2019.01.072.

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33

Orel, A. E., and T. N. Rescigno. "Photoionization of ammonia." Chemical Physics Letters 269, no. 3-4 (May 1997): 222–26. http://dx.doi.org/10.1016/s0009-2614(97)00283-2.

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34

Syage, Jack A., Karl A. Hanold, Thomas C. Lynn, Julie A. Horner, and Rohan A. Thakur. "Atmospheric pressure photoionization." Journal of Chromatography A 1050, no. 2 (October 2004): 137–49. http://dx.doi.org/10.1016/j.chroma.2004.08.033.

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35

Dolder, Ken. "Photodissociation and photoionization." Endeavour 10, no. 1 (January 1986): 52. http://dx.doi.org/10.1016/0160-9327(86)90064-5.

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36

Fischer, Charlotte Froese, and Hari P. Saha. "Photoionization of magnesium." Canadian Journal of Physics 65, no. 7 (July 1, 1987): 772–76. http://dx.doi.org/10.1139/p87-113.

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Photoionization from the 3s subshell of magnesium is investigated in the energy region near threshold where several resonances have been observed. Theoretical cross sections are reported. The latter have been computed using the multi-configuration Hartree–Fock approximation extended to include a continuum function. Results are compared with other theories and experiment.

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37

Mustafaev, A. S., I. V. Rastvorova, S. S. Podenko, and A. B. Tsyganov. "Photoionization microplasma sensor." Journal of Physics: Conference Series 929 (November 2017): 012105. http://dx.doi.org/10.1088/1742-6596/929/1/012105.

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38

Pireaux, J. J. "Laser photoionization spectroscopy." Journal of Molecular Catalysis 52, no. 3 (July 1989): 397–98. http://dx.doi.org/10.1016/0304-5102(89)85049-7.

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39

Burshtein, A. I., and V. A. Morozov. "Activationless photoionization reactions." Chemical Physics Letters 165, no. 5 (January 1990): 432–36. http://dx.doi.org/10.1016/0009-2614(90)85455-l.

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Khachalov, M. B. "Photoionization of air." High Temperature 38, no. 2 (March 2000): 314–16. http://dx.doi.org/10.1007/bf02755961.

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Qi, Fei, Shihe Yang, Liusi Sheng, Hui Gao, Yunwu Zhang, and Shuqin Yu. "Vacuum ultraviolet photoionization and dissociative photoionization of W(CO)6." Journal of Chemical Physics 107, no. 24 (December 22, 1997): 10391–98. http://dx.doi.org/10.1063/1.474202.

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Chiang, Su-Yu, Yung-Sheng Fang, Mohammed Bahou, and K. Sankaran. "Experiments and Calculations on Photoionization and Dissociative Photoionization of CH2CO." Journal of the Chinese Chemical Society 51, no. 4 (August 2004): 681–88. http://dx.doi.org/10.1002/jccs.200400103.

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Pan, Yang, Li-dong Zhang, Hui-jun Guo, Hao Yin, and Fei Qi. "Photoionization and Dissociative Photoionization Study of Cholesterol by IR Laser Desorption/Tunable Synchrotron VUV Photoionization Mass Spectrometry." Chinese Journal of Chemical Physics 22, no. 2 (April 2009): 129–33. http://dx.doi.org/10.1088/1674-0068/22/02/129-133.

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Allen, M. G., M. A. Dopita, and Z. I. Tsvetanov. "Excitation Mechanisms in Seyfert Galaxies." International Astronomical Union Colloquium 159 (1997): 392–93. http://dx.doi.org/10.1017/s0252921100040550.

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The excitation mechanism of the extended emission-line regions (EELRs) in Seyfert galaxies is commonly thought to be nuclear photoionization. However, some Seyfert galaxies have EELRs with disturbed kinematics, outflows, and morphology which is indicative of interaction between radio plasma and the ISM of the host galaxy. In these cases shock excitation must also be considered (BickneU 1993).To investigate the importance of shocks and photoionization, we have taken two approaches: mapping the spatial dependence of the line ratios, and using UV line ratios which are sensitive discriminants between shocks and photoionization.

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Измайлов, А. Ч. "Внутридоплеровские резонансы, обусловленные фотоионизацией атомов в тонких газовых ячейках." Оптика и спектроскопия 130, no. 3 (2022): 353. http://dx.doi.org/10.21883/os.2022.03.52161.2785-21.

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By analogy with the well-tested method of high-resolution spectroscopy in thin gas cells for the processes of optical pumping of atoms, this work shows the possibility of detecting narrow sub-Doppler optical resonances caused directly by straight photoionization of atoms (or molecules) in such cells. The structure of the established nontrivial resonances substantially depends on the probability of photoionization of atoms and dimensions of such a cell, the internal thickness of which is many times smaller than its diameter. Of particular interest is the broadening of the considered sub-Doppler resonances, which is determined directly by the photoionization cross section of atoms and the intensity of radiation causing ionization. Under certain conditions, such photoionization broadening can be measured experimentally with high accuracy, as a result of which it is possible to obtain new important information about ionization processes in atoms and molecules.

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Zhu, Peixin, Lisa J. Kewley, and Ralph S. Sutherland. "A New Photoionization Model of the Narrow-line Region in Active Galactic Nuclei." Astrophysical Journal 954, no. 2 (September 1, 2023): 175. http://dx.doi.org/10.3847/1538-4357/acd757.

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Abstract The photoionization model of narrow-line regions in active galactic nuclei (AGNs) has been investigated for decades. Many published models are restricted to simple linear scaling abundance relations, dust-free assumption, uniform AGN radiation field, and using one specific photoionization code, which restricts them from providing a satisfactory prediction on a broad range of AGN observations. Through a comprehensive investigation, here we present how the choice of abundance scaling relations, dust inclusion, AGN radiation fields, and different photoionization codes CLOUDY and MAPPINGS affect the predictions on the strength of strong UV, optical, and infrared emission lines. We find the dust-depleted radiation-pressure-dominated AGN model built with the latest nonlinear abundance sets and photoionization code MAPPINGS V are consistent with AGN observations across a broad range of wavelengths. We also assess new potential H ii-AGN separation diagrams in the optical and UV wavelengths.

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Allende Prieto, Carlos. "The Shapes of Stellar Spectra." Atoms 11, no. 3 (March 20, 2023): 61. http://dx.doi.org/10.3390/atoms11030061.

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Stellar atmospheres separate the hot and dense stellar interiors from the emptiness of space. Radiation escapes from the outermost layers of a star, carrying direct physical information. Underneath the atmosphere, the very high opacity keeps radiation thermalized and resembling a black body with the local temperature. In the atmosphere the opacity drops, and radiative energy leaks out, which is redistributed in wavelength according to the physical processes by which matter and radiation interact, in particular photoionization. In this article, I will evaluate the role of photoionization in shaping the stellar energy distribution of stars. To that end, I employ simple, state-of-the-art plane-parallel model atmospheres and a spectral synthesis code, dissecting the effects of photoionization from different chemical elements and species, for stars of different masses in the range of 0.3 to 2 M⊙. I examine and interpret the changes in the observed spectral energy distributions of the stars as a function of the atmospheric parameters. The photoionization of atomic hydrogen and H− are the most relevant contributors to the continuum opacity in the optical and near-infrared regions, while heavier elements become important in the ultraviolet region. In the spectra of the coolest stars (spectral types M and later), the continuum shape from photoionization is no longer recognizable due to the accumulation of lines, mainly from molecules. These facts have been known for a long time, but the calculations presented provide an updated quantitative evaluation and insight into the role of photoionization on the structure of stellar atmospheres.

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Wang, Dehua, Shaohao Cheng, Qiang Chen, and Zhaohang Chen. "DC field microscopy of Rydberg Li atoms." Canadian Journal of Physics 94, no. 6 (June 2016): 548–57. http://dx.doi.org/10.1139/cjp-2015-0791.

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The DC field microscopy of Rydberg Li atoms has been studied on the basis of the semiclassical theory for the first time. In particular, we discuss the atomic core scattering effect in the ionization dynamics of the Rydberg Li atom. Unlike the case of the photoionization of a Rydberg H atom in an electric field, where the photoionization microscopy interference patterns are mainly caused by the Coulomb scattering and the electric field potential, for the photoionization of a Rydberg Li atom in an electric field, the influence of the atomic core scattering effect on the photoionization microscopy interference patterns plays an important role. In addition, the structure of the interference pattern, which contains the spatial component of the electronic wave function, evolves smoothly with the electron energy above the saddle point energy. The observed oscillatory patterns in the electron probability density distributions on the detector plane are interpreted within the framework of the semiclassical approximation, which can be considered as a manifestation of interference between various electron trajectories arriving at a given point from the atom to the detector plane. This study provides some reference values for future experimental research on photoionization microscopy of the non-hydrogen Rydberg atoms in the presence of external fields.

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Schippers, Stefan, Sebastian Stock, Ticia Buhr, Alexander Perry-Sassmannshausen, Simon Reinwardt, Michael Martins, Alfred Müller, and Stephan Fritzsche. "Near K-edge Photoionization and Photoabsorption of Singly, Doubly, and Triply Charged Silicon Ions." Astrophysical Journal 931, no. 2 (May 27, 2022): 100. http://dx.doi.org/10.3847/1538-4357/ac6874.

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Abstract Experimental and theoretical results are presented for double, triple, and quadruple photoionization of Si+ and Si2+ ions and for double photoionization of Si3+ ions by a single photon. The experiments employed the photon–ion merged-beams technique at a synchrotron light source. The experimental photon-energy range 1835–1900 eV comprises resonances associated with the excitation of a 1s electron to higher subshells and subsequent autoionization. Energies, widths, and strengths of these resonances are extracted from high-resolution photoionization measurements, and the core-hole lifetime of K-shell ionized neutral silicon is inferred. In addition, theoretical cross sections for photoabsorption and multiple photoionization were obtained from large-scale multiconfiguration Dirac–Hartree–Fock calculations. The present calculations agree with the experiment much better than previously published theoretical results. The importance of an accurate energy calibration of laboratory data is pointed out. The present benchmark results are particularly useful for discriminating between silicon absorption in the gaseous and in the solid component (dust grains) of the interstellar medium.

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Miranda, Adelaide, and Pieter A. A. De Beule. "Atmospheric Photoionization Detector with Improved Photon Efficiency: A Proof of Concept for Application of a Nanolayer Thin-Film Electrode." Sensors 21, no. 22 (November 20, 2021): 7738. http://dx.doi.org/10.3390/s21227738.

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Atmospheric photoionization is a widely applied soft ionization mechanism in gas sensing devices for the detection of volatile organic compounds in ambient air. Photoionization is typically induced by low-pressure Vacuum Ultraviolet (VUV) lamps with MgF2 or LiF lamp surface windows depending on the gas fill and the required wavelength transmission window. These lamps are known to exhibit gradually reduced VUV transmission due to hydrocarbon contamination. LiF surface windows are known to be especially problematic due to their hygroscopic nature, reducing VUV lamp lifetime to a mere 100 h, approximately. Here, we present a new design for the electrode of a photoionization detector based on thin-film technology. By replacing the commonplace metal grid electrode’s VUV lamp surface window with a chromium/gold thin film we obtain a doubling of photon efficiency for photoionization. Replacing the hygroscopic LiF lamp window surface with a metallic layer additionally offers the possibility to vastly increase operational lifetime of low-pressure Argon VUV lamps.

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