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Title: Inelastic low-energy collisions of electrons with HeH + : Rovibrational excitation and dissociative recombination

Authors:
 [1];  [2]
  1. J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Dolejškova 3, 182 23 Prague 8, Czech Republic
  2. Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1373985
Grant/Contract Number:
SC0010545
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 147; Journal Issue: 5; Related Information: CHORUS Timestamp: 2018-02-14 12:11:21; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics
Country of Publication:
United States
Language:
English

Citation Formats

Čurík, Roman, and Greene, Chris H. Inelastic low-energy collisions of electrons with HeH + : Rovibrational excitation and dissociative recombination. United States: N. p., 2017. Web. doi:10.1063/1.4994921.
Čurík, Roman, & Greene, Chris H. Inelastic low-energy collisions of electrons with HeH + : Rovibrational excitation and dissociative recombination. United States. doi:10.1063/1.4994921.
Čurík, Roman, and Greene, Chris H. 2017. "Inelastic low-energy collisions of electrons with HeH + : Rovibrational excitation and dissociative recombination". United States. doi:10.1063/1.4994921.
@article{osti_1373985,
title = {Inelastic low-energy collisions of electrons with HeH + : Rovibrational excitation and dissociative recombination},
author = {Čurík, Roman and Greene, Chris H.},
abstractNote = {},
doi = {10.1063/1.4994921},
journal = {Journal of Chemical Physics},
number = 5,
volume = 147,
place = {United States},
year = 2017,
month = 8
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on August 4, 2018
Publisher's Accepted Manuscript

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  • Electron-molecule scattering information is important in studying chemical reactions in the upper atmosphere, in optimizing gas laser performance, and in maximizing the efficiency of magneto hydrodynamic power generation. The vibrational excitation of N[sub 2]O and OCS following excimer laser photolysis of I[sub 2] in a low-pressure mixture of I[sub 2] and N[sub 2]O of I[sub 2] and OCS has been studied using an excimer laser photolysis/diode laser probe technique. Vibrational excitation probabilities and nascent rotational distributions have been obtained for a number of low-lying vibrational levels. In addition, measurements of the transient N[sub 2]O and OCS line widths have beenmore » performed for the majority of the rovibrational states probed. Although a relatively large amount of vibrational excitation has been observed in N[sub 2]O and OCS, negligible energy transfer to the translational and rotational degrees of freedom of the products is observed. The results are consistent with the production of vibrationally excited N[sub 2]O and OCS molecules via collisions with low-energy electrons arising from multiphoton ionization of I[sub 2]. 37 refs., 9 figs., 2 tabs.« less
  • The dissociative recombination (DR) of {sup 3}He {sup 4}He{sup +} has been investigated at the heavy-ion Test Storage Ring (TSR) in Heidelberg by observing neutral products from electron-ion collisions in a merged beams configuration at relative energies from near-zero (thermal electron energy about 10 meV) up to 40 eV. After storage and electron cooling for 35 s, an effective DR rate coefficient at near-zero energy of 3x10{sup -9} cm{sup 3}s{sup -1} is found. The temporal evolution of the neutral product rates and fragment imaging spectra reveals that the populations of vibrational levels in the stored ion beam are nonthermal withmore » fractions of {approx}0.1-1 % in excited levels up to at least v=4, having a significant effect on the observed DR signals. With a pump-probe-type technique using DR fragment imaging while switching the properties of the electron beam, the vibrational excitation of the ions is found to originate mostly from ion collisions with the residual gas. Also, the temporal evolution of the DR signals suggests that a strong electron induced rotational cooling occurs in the vibrational ground state, reaching a rotational temperature near or below 300 K. From the absolute rate coefficient and the shape of the fragment imaging spectrum observed under stationary conditions, the DR rate coefficient from the vibrational ground state is determined; converted to a thermal electron gas at 300 K it amounts to (3.3{+-}0.9)x10{sup -10} cm{sup 3}s{sup -1}. The corresponding branching ratios from v=0 to the atomic final states are found to be (3.7{+-}1.2) % for 1s2s {sup 3}S,(37.4{+-}4.0) % for 1s2s {sup 1}S,(58.6{+-}5.2) % for 1s2p {sup 3}P, and (2.9{+-}3.0) % for 1s2p {sup 1}P. A DR rate coefficient in the range of 2x10{sup -7} cm{sup 3}s{sup -1} or above is inferred for vibrational levels v=3 and higher. As a function of the collision energy, the measured DR rate coefficient displays a structure around 0.2 eV. At higher energies, it has one smooth peak around 7.3 eV and a highly structured appearance at 15-40 eV. The small size of the observed effective DR rate coefficient at near-zero energy indicates that the electron induced rotational cooling is due to inelastic electron-ion collisions and not due to selective depletion of rotational levels by DR.« less
  • A semiempirical analysis is made of the contributions of the two lowest resonant states to dissociative attachment and vibrational excitation in low-energy collisions of electrons with H/sub 2/ and D/sub 2/. The resonance models are based both on ab initio calculations and on fits to experimental data. The dissociative-attachment cross section near threshold is enhanced significantly by vibrational or rotational excitation of the initial molecule. Near 10 eV, contributions from both resonances are required to explain the observed cross sections for vibrational excitation.
  • Dissociative recombination of H/sub 2//sup +/ by collisions with slow electrons is investigated by the multichannel quantum defect theory. (AIP)