scholarly journals Vibrational Quenching of Weakly Bound Cold Molecular Ions Immersed in Their Parent Gas

2020 ◽  
Vol 10 (7) ◽  
pp. 2371 ◽  
Author(s):  
Krzysztof Jachymski ◽  
Florian Meinert
Keyword(s):  
Product Distribution ◽  
Molecular Ions ◽  
Inelastic Collisions ◽  
Inelastic Process ◽  
Distorted Wave ◽  
Distorted Wave Born Approximation ◽  
Weakly Bound ◽  
Molecular Ion ◽  
Background Gas ◽  
Range Part

Hybrid ion–atom systems provide an excellent platform for studies of state-resolved quantum chemistry at low temperatures, where quantum effects may be prevalent. Here we study theoretically the process of vibrational relaxation of an initially weakly bound molecular ion due to collisions with the background gas atoms. We show that this inelastic process is governed by the universal long-range part of the interaction potential, which allows for using simplified model potentials applicable to multiple atomic species. The product distribution after the collision can be estimated by making use of the distorted wave Born approximation. We find that the inelastic collisions lead predominantly to small changes in the binding energy of the molecular ion.

Resonance recombination of spin-polarized atomic hydrogen at low temperatures

1988 ◽  
Vol 66 (5) ◽  
pp. 405-413 ◽  
Author(s):  
M. W. Reynolds ◽  
W. N. Hardy
Keyword(s):  
Cross Section ◽  
Dissociation Energy ◽  
Born Approximation ◽  
Atomic Hydrogen ◽  
Proton Exchange ◽  
Distorted Wave ◽  
Distorted Wave Born Approximation ◽  
Weakly Bound ◽  
Coupled Channels ◽  
Spin Polarized

In sufficiently large magnetic fields, the weakly bound levels of H2 acquire finite lifetimes owing to hyperfine predissociation and become manifest as scattering resonances in spin-polarized atomic hydrogen (H↓). In this work we investigate in detail the contribution to the reaction kinetics in H↓ due to the resonance, denoted [Formula: see text], arising from the predissociation of the (v,J) = (14,4) level of H2. To characterize the formation and disintegration of [Formula: see text], we calculate the predissociation as a function of both the applied magnetic field and the dissociation energy, D, of the level. Recombination occurs when [Formula: see text] is stabilized in collisions that cause transitions to lower molecular levels. For low H↓, densities, collisions with atoms of the saturated 4He vapour dominate; we calculate the cross section in the distorted wave Born approximation and also use a coupled-channels approach. At higher densities, stabilization occurs in collisions with H↓ as well; the effect of proton exchange between the atom and the molecule is derived. Previous experiments, analyzed neglecting proton exchange, are reanalyzed including this; the dissociation energy D is not as well determined by the data as was previously thought. Prospects for future experiments are discussed.

Rotationally inelastic collisions of orbitally degenerate molecules; maser action in OH and CH

1979 ◽  
Vol 368 (1732) ◽  
pp. 99-123 ◽  
Keyword(s):  
Low Temperature ◽  
Cross Section ◽  
Cross Sections ◽  
Born Approximation ◽  
Open Shell ◽  
Inelastic Collisions ◽  
Distorted Wave ◽  
Distorted Wave Born Approximation ◽  
The Cross ◽  
Maser Action

The theory of rotationally inelastic collisions between orbitally degenerate diatomic molecules and open-shell atoms is developed. Because of the orbital degeneracy two or more electronic potential energy surfaces are involved. Matrix elements of the interaction Hamiltonian are given, hyperfine coupling in the diatomic molecule also being included. From these it is apparent th at the parity of the initial Λ -doublet level will influence the inelastic scattering cross section for poles of interaction λ such that λ ≥ 2 Λ .An expression is developed for state-to-state cross sections using the restricted distorted wave Born approximation. A set of branching coefficients is defined which allows the representation of the parity dependence of the cross section in a simple parametric form. The theory is applied to collisional pumping as an excitation mechanism for interstellar maser action of OH and CH through the inversion of Λ -doublet populations. H atoms, H 2 , He, H + and H + 3 are considered as collision partners. Branching coefficients are tabulated for a variety of excitations from the rotational ground states. The sense of the parity dependence of the cross sections arises from the gross features of the interaction potential at medium and long range, and can be deduced using approximate theoretical surfaces or empirical models. An analogy is drawn with the experimental rates of rotational energy transfer in the closely related system H + NH 2 (Ã, 2 A 1 ), which are ca. 10 -9 cm 3 s -1 , and which have been successfully interpreted using the distorted wave Born approximation. These results are used to give qualitative predictions of population inversion in the Λ -doublets of OH, OD and CH in interstellar clouds. We show th at the ground J = 1 ½ doublet, and excited doublets of the F 1 manifold, of OH and OD will be inverted following collisions with H, H 2 and He. The J = 1/2 doublet of the F 2 manifold of OH and OD will be inverted by collisions with the ions H + and H + 3 . In CH low temperature collisions with H atoms will result in inversion of the ground J = 1 ½ doublet. Collisions with H 2 and He at low temperature result in cooling of the doublet. Implications for maser action are briefly discussed.

Multi-channel distorted-wave Born approximation for rovibrational transition rates in molecular collisions

2021 ◽  
Vol 155 (3) ◽  
pp. 034105
Author(s):  
Taha Selim ◽  
Arthur Christianen ◽  
Ad van der Avoird ◽  
Gerrit C. Groenenboom
Keyword(s):  
Born Approximation ◽  
Transition Rates ◽  
Distorted Wave ◽  
Distorted Wave Born Approximation ◽  
Molecular Collisions

scholarly journals A Complete CDW Theory for the Single Ionization of Multielectronic Atoms by Bare Ion Impact

Atoms ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 3
Author(s):  
Juan M. Monti ◽  
Michele A. Quinto ◽  
Roberto D. Rivarola
Keyword(s):  
Transition Amplitude ◽  
Emission Spectra ◽  
Heavy Ion ◽  
Distorted Wave ◽  
Single Ionization ◽  
Complete Form ◽  
Active Electron ◽  
Ion Impact ◽  
Range Part ◽  
The Continuum

A complete form of the post version of the continuum distorted wave (CDW) theory is used to investigate the single ionization of multielectronic atoms by fast bare heavy ion beams. The influence of the non-ionized electrons on the dynamic evolution is included through a residual target potential considered as a non-Coulomb central potential through a GSZ parametric one. Divergences found in the transition amplitude containing the short-range part of the target potential are avoided by considering, in that term exclusively, an eikonal phase instead of the continuum factor as the initial channel distortion function. In this way, we achieve the inclusion of the interaction between the target active electron and the residual target, giving place to a more complete theory. The present analysis is supported by comparisons with existing experimental electron emission spectra and other distorted wave theories.

Analysing powers and differential cross sections of (3He,p) reactions on 6Li and 7Li at low energy

1995 ◽  
Vol 73 (1-2) ◽  
pp. 74-84 ◽  
Author(s):  
D. Baddou ◽  
C. Rioux ◽  
R. J. Slobodrian ◽  
J. M. Nelson
Keyword(s):  
Cross Sections ◽  
Differential Cross ◽  
Born Approximation ◽  
Low Energy ◽  
Angular Distributions ◽  
Differential Cross Sections ◽  
Distorted Wave ◽  
Distorted Wave Born Approximation ◽  
Nucleon Transfer ◽  
Cluster Transfer

Angular distributions of the differential cross sections and analysing powers were measured at an energy of 4.6 MeV. The results are compared with the distorted wave Born approximation predictions for two-nucleon transfer and for a deuteron-cluster transfer. The agreement is qualitative at best, and a discussion of alternatives to improve it is presented.

Field desorption mass spectrometry of carboxylic acids: characteristic spectra and analysis of mixtures and impure samples

1978 ◽  
Vol 56 (10) ◽  
pp. 1372-1377 ◽  
Author(s):  
Gordon Walter Wooo ◽  
Emily Jane Oldenburg ◽  
Pui-Yan Lau ◽  
Donna Lee Wade
Keyword(s):  
Carboxylic Acids ◽  
Dicarboxylic Acids ◽  
Cross Product ◽  
Molecular Ions ◽  
Base Peak ◽  
Field Desorption ◽  
Technical Grade ◽  
Molecular Ion ◽  
Field Desorption Mass Spectrometry ◽  
Anode Temperature

Field desorption mass spectra were obtained for a variety of saturated and unsaturated carboxylic acids containing 12 or more carbons. At best anode temperature molecular ions were dominant and small peaks representing [M + 1]+, [2M + 1]+, [M − 17]+, and [Formula: see text] were present in several compounds. At higher temperatures several novel ions were found, including one corresponding to [2M + 1 – 18]+ which may represent anhydride formation. In a mixture of cis-5-eicosenoic and elaidic acids each molecular ion desorbed as expected but at higher temperatures the three possible anhydride ions appeared, with the cross product [M1 + M2 + 1 − H2O]+ as the base peak. Isomeric hydroxystearic acids (2-OH, 12-OH, 17-OH) gave predominantly ions in the molecular ion region with some differences in spectra which may relate to structure. Apparent polyester formation has been observed in 3-hydroxypropanoic acid where ions of the general formula [xM − (x − 1)H2O + H]+ with x = 2, 3, … 13 were found. Several other hydroxyacids show dimer formation and lactic acid has ions up to x = 5 in the above formula. Two of four technical grade dicarboxylic acids tested were seriously contaminated by sodium ions and gave useful spectra only after extraction by dibenzo-18-crown-6 ether. After this treatment both adipic and azelaic acid have [M + 1]+ as base peak, although adipic acid decarboxylates readily ([Formula: see text] = 74%) Other technical grade acids showed the presence of homologues and related structures as impurities.

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