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Title: Yield of electronically excited CN molecules from the dissociative recombination of HNC{sup +} with electrons

Abstract

The authors have studied CN(B-X) and CN(A-X) emissions produced by the dissociative recombination of HNC{sup +} ions with thermal electrons in a flowing afterglow experiment. A separate drift tube study showed that the reaction Ar{sup +}+HCN, the precursor reaction used in the flow-tube experiment, produces predominantly HNC{sup +} rather than the more energetic HCN{sup +} isomer. Models simulating the ion-chemical processes, diffusion, and gas mixing in the afterglow plasma were fitted to observed position dependent CN(A-X) and CN(B-X) band intensities. Absolute yields of CN(B) and CN(A) were then obtained by comparing the CN band intensities to those of CO bands produced by recombination of CO{sub 2}{sup +} ions. It was concluded that the 300 K recombination coefficient of HNC{sup +} is close to 2x10{sup -7} cm{sup 3} s{sup -1}, that CN(B) is formed with a yield of 0.22{+-}0.08 and CN(A) with a yield of 0.14{+-}0.05. By comparison to synthetic spectra, the rotational temperature of CN(B) was estimated to be approximately 2500 K. It was also found that recombination produces CN(B) and CN(A) with far greater vibrational excitation than would be expected from the ''impulse model'' of Bates [Mon. Not. R. Astron. Soc. 263, 369 (1993)].

Authors:
; ; ;  [1];  [2]
  1. Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20991247
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 126; Journal Issue: 15; Other Information: DOI: 10.1063/1.2715945; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; AFTERGLOW; CARBON COMPOUNDS; CATIONS; DIFFUSION; DISSOCIATION; EXCITATION; HYDROGEN COMPOUNDS; ION-MOLECULE COLLISIONS; NITROGEN COMPOUNDS; RECOMBINATION; ROTATIONAL STATES; SPECTRA

Citation Formats

Rosati, Richard E., Pappas, Daphne, Johnsen, Rainer, Golde, Michael F., and Department of Chemistry, University of Pittsburgh, Pennsylvania 15260. Yield of electronically excited CN molecules from the dissociative recombination of HNC{sup +} with electrons. United States: N. p., 2007. Web. doi:10.1063/1.2715945.
Rosati, Richard E., Pappas, Daphne, Johnsen, Rainer, Golde, Michael F., & Department of Chemistry, University of Pittsburgh, Pennsylvania 15260. Yield of electronically excited CN molecules from the dissociative recombination of HNC{sup +} with electrons. United States. doi:10.1063/1.2715945.
Rosati, Richard E., Pappas, Daphne, Johnsen, Rainer, Golde, Michael F., and Department of Chemistry, University of Pittsburgh, Pennsylvania 15260. Sat . "Yield of electronically excited CN molecules from the dissociative recombination of HNC{sup +} with electrons". United States. doi:10.1063/1.2715945.
@article{osti_20991247,
title = {Yield of electronically excited CN molecules from the dissociative recombination of HNC{sup +} with electrons},
author = {Rosati, Richard E. and Pappas, Daphne and Johnsen, Rainer and Golde, Michael F. and Department of Chemistry, University of Pittsburgh, Pennsylvania 15260},
abstractNote = {The authors have studied CN(B-X) and CN(A-X) emissions produced by the dissociative recombination of HNC{sup +} ions with thermal electrons in a flowing afterglow experiment. A separate drift tube study showed that the reaction Ar{sup +}+HCN, the precursor reaction used in the flow-tube experiment, produces predominantly HNC{sup +} rather than the more energetic HCN{sup +} isomer. Models simulating the ion-chemical processes, diffusion, and gas mixing in the afterglow plasma were fitted to observed position dependent CN(A-X) and CN(B-X) band intensities. Absolute yields of CN(B) and CN(A) were then obtained by comparing the CN band intensities to those of CO bands produced by recombination of CO{sub 2}{sup +} ions. It was concluded that the 300 K recombination coefficient of HNC{sup +} is close to 2x10{sup -7} cm{sup 3} s{sup -1}, that CN(B) is formed with a yield of 0.22{+-}0.08 and CN(A) with a yield of 0.14{+-}0.05. By comparison to synthetic spectra, the rotational temperature of CN(B) was estimated to be approximately 2500 K. It was also found that recombination produces CN(B) and CN(A) with far greater vibrational excitation than would be expected from the ''impulse model'' of Bates [Mon. Not. R. Astron. Soc. 263, 369 (1993)].},
doi = {10.1063/1.2715945},
journal = {Journal of Chemical Physics},
number = 15,
volume = 126,
place = {United States},
year = {Sat Apr 21 00:00:00 EDT 2007},
month = {Sat Apr 21 00:00:00 EDT 2007}
}
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  • The reaction dynamics of the five-atom system, H + (CN){sub 2}, was investigated by probing the minor product channel producing the transient HNC molecule. The complete initial energy disposition, translation, rotation, and vibration was determined for the HNC(0v{sup 1}{sub 2} 0), v{sup 1}{sub 2} = 0{sup 0},1{sup -1}, product. The reaction was studied under bulk conditions and was initiated by energetic H atoms with a mean translational energy of 92 kJ mol{sup -1}. The HNC molecule was monitored by time- and frequency-resolved absorption spectroscopy with sub-Doppler resolution. The initial rotational state distribution of each HNC(0 v{sup 1}{sub 2} 0) vibrationalmore » level was measured and found to be well-described by a Boltzmann distribution. Only two vibrational levels were detected so that the initial HNC product vibrational level distribution was determined as well. The absolute reaction cross section for the title reaction was measured to be 2 x 10{sup -18} cm{sup -2} for H atoms with a nominal translational energy of 113 kJ mol.{sup -1}.« less
  • The yield of metastable oxygen atoms through dissociative recombination of O{sup +}{sub 2} ions with electrons has been studied using a plasma flow tube experiment. For O{sup +}{sub 2} with high vibrational excitation (around {ital v}=9) it was found that half of the oxygen atoms are formed on the O({sup 1}{ital D}) state and that the branching ratio toward O({sup 1}{ital S}) is large ({similar to}0.4). Using Xe{sup +} instead of Ar{sup +} as precursor ions, it was shown that the O({sup 1}{ital S}) yield is much less for ions with low vibrational excitation. However, the present experimental results aremore » not compatible with the extremely low theoretical value of this yield which was reported recently for O{sup +}{sub 2} ({ital v}=0).« less
  • The process of dissociative recombination with production of strongly excited atoms in collisions between electrons of energy 1--13 eV and molecular ions is considered. The recombination cross sections are calculated for the system e+H/sub 2//sup ts+/ (D/sub 2//sup ts+/) with formation of excited atoms in states with n> or =3 for different vibrational states of H/sub 2//sup ts+/ (D/sub 2//sup ts+/). The calculation results are compared with the available experimental measurements. The transition from the quantum description of the motion of the nuclei in dissociative recombination to the classical description is indicated.