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Title: Ionization and temperature dependent attachment cross section measurements in C/sub 3/F/sub 8/ and C/sub 2/H/sub 3/Cl

Abstract

Total ionization and attachment cross sections have been measured in C/sub 3/F/sub 8/ at 330 K using an electron beam and a total ion collection technique, calibrated by similar measurements on N/sub 2/O and Xe. Our total ionization cross section is similar in general shape to a previous measurement of this type, but with typically half the magnitude. The ionization threshold cannot be accurately derived from these measurements, due to severe upward curvature immediately above threshold. The positive-ion signal rises above the background at 13.0 +- 0.1 eV, to be regarded as a lower limit to the true threshold. An overall ionization cross section with a threshold at 13.3 eV is recommended, based on threshold data from photoelectron spectroscopy and the present data between 14 and 80 eV. The room temperature total attachment cross section peaks at 2.8 eV with a value of 1.75 x 10/sup -17/ cm/sup 2/. This is 14 times smaller than the only other measurement of this type we are aware of. There is much better agreement with two more recently reported values unfolded from swarm experiments. The temperature dependence of the predominant dissociative attachment process, involving F/sup -/ production, was studied in a different apparatusmore » using a mass filter and ion pulse counting. At 730 K the peak cross section has increased by approx.60% and the threshold is lower by 1.1 eV. This second type of measurement was used to study the predominant dissociative attachment process in C/sub 2/H/sub 3/Cl, involving Cl/sup -/ production. At 290 K this has a threshold at 0.85 eV and a peak at 1.35 eV of 3.2 x 10/sup -17/ cm/sup 2/, in good agreement with recent work elsewhere. At 850 K the cross section at the peak is 2.6 larger, and lower in energy by 0.33 eV, while at 0 eV it has reached 6 x 10/sup -18/ cm/sup 2/. At higher temperatures effects ascribed to thermal dissociation of the C/sub 2/H/sub 3/Cl were observed.« less

Authors:
;
Publication Date:
Research Org.:
Westinghouse RandD Center, 1310 Beulah Road, Pittsburgh, Pennsylvania 15235
OSTI Identifier:
6532462
Resource Type:
Journal Article
Journal Name:
J. Chem. Phys.; (United States)
Additional Journal Information:
Journal Volume: 90:5
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; CHLORINATED ALIPHATIC HYDROCARBONS; ELECTRON ATTACHMENT; IONIZATION; FLUORINATED ALIPHATIC HYDROCARBONS; PLASMA SWITCHES; DESIGN; ADDITIVES; DISSOCIATION; ELECTRON BEAMS; HIGH TEMPERATURE; MEDIUM TEMPERATURE; TEMPERATURE DEPENDENCE; TOTAL CROSS SECTIONS; BEAMS; CROSS SECTIONS; ELECTRICAL EQUIPMENT; EQUIPMENT; HALOGENATED ALIPHATIC HYDROCARBONS; LEPTON BEAMS; ORGANIC CHLORINE COMPOUNDS; ORGANIC COMPOUNDS; ORGANIC FLUORINE COMPOUNDS; ORGANIC HALOGEN COMPOUNDS; PARTICLE BEAMS; SWITCHES; 640304* - Atomic, Molecular & Chemical Physics- Collision Phenomena

Citation Formats

Chantry, P J, and Chen, C L. Ionization and temperature dependent attachment cross section measurements in C/sub 3/F/sub 8/ and C/sub 2/H/sub 3/Cl. United States: N. p., 1989. Web.
Chantry, P J, & Chen, C L. Ionization and temperature dependent attachment cross section measurements in C/sub 3/F/sub 8/ and C/sub 2/H/sub 3/Cl. United States.
Chantry, P J, and Chen, C L. 1989. "Ionization and temperature dependent attachment cross section measurements in C/sub 3/F/sub 8/ and C/sub 2/H/sub 3/Cl". United States.
@article{osti_6532462,
title = {Ionization and temperature dependent attachment cross section measurements in C/sub 3/F/sub 8/ and C/sub 2/H/sub 3/Cl},
author = {Chantry, P J and Chen, C L},
abstractNote = {Total ionization and attachment cross sections have been measured in C/sub 3/F/sub 8/ at 330 K using an electron beam and a total ion collection technique, calibrated by similar measurements on N/sub 2/O and Xe. Our total ionization cross section is similar in general shape to a previous measurement of this type, but with typically half the magnitude. The ionization threshold cannot be accurately derived from these measurements, due to severe upward curvature immediately above threshold. The positive-ion signal rises above the background at 13.0 +- 0.1 eV, to be regarded as a lower limit to the true threshold. An overall ionization cross section with a threshold at 13.3 eV is recommended, based on threshold data from photoelectron spectroscopy and the present data between 14 and 80 eV. The room temperature total attachment cross section peaks at 2.8 eV with a value of 1.75 x 10/sup -17/ cm/sup 2/. This is 14 times smaller than the only other measurement of this type we are aware of. There is much better agreement with two more recently reported values unfolded from swarm experiments. The temperature dependence of the predominant dissociative attachment process, involving F/sup -/ production, was studied in a different apparatus using a mass filter and ion pulse counting. At 730 K the peak cross section has increased by approx.60% and the threshold is lower by 1.1 eV. This second type of measurement was used to study the predominant dissociative attachment process in C/sub 2/H/sub 3/Cl, involving Cl/sup -/ production. At 290 K this has a threshold at 0.85 eV and a peak at 1.35 eV of 3.2 x 10/sup -17/ cm/sup 2/, in good agreement with recent work elsewhere. At 850 K the cross section at the peak is 2.6 larger, and lower in energy by 0.33 eV, while at 0 eV it has reached 6 x 10/sup -18/ cm/sup 2/. At higher temperatures effects ascribed to thermal dissociation of the C/sub 2/H/sub 3/Cl were observed.},
doi = {},
url = {https://www.osti.gov/biblio/6532462}, journal = {J. Chem. Phys.; (United States)},
number = ,
volume = 90:5,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 1989},
month = {Wed Mar 01 00:00:00 EST 1989}
}