ABSTRACT
The threshold energy for vibrational excitation (ν = 1) is 0328 eV and shape resonance is observed at 09 eVTable 192 and Figure 191 (Rohr, 1978) show these data
Dissociative attachment according to reaction 191 is the dominant process
HBr + e → H + Br− (191)
191 Selected References for Data 131 192 Vibrational Excitation Cross Section131 193 Attachment Processes131 194 Attachment Cross Section 132 195 Attachment Rate Constants 133 References 133
TABLE 19.1 Selected References for Data on HBr
Parameter Range: eV, (Td), [K] Reference
Qv 0-10 Rohr (1978) ka [48-170] Speck et al. (2001) ka 0-2 Wang and Lee (1988) ka [300, 515] Smith and Adams (1987) ka [300, 515] Adams et al. (1986) AP 0-1 Ziesel et al. (1975) ka 0-20 Christophorou et al. (1968) AP — Frost and McDowell (1958)
Note:AP = attachment process; ka = attachment rate constant; Qv = vibrational cross section Bold font indicates experimental study
TABLE 19.2 Vibrational Excitation for HBr
Threshold Resonance (ν = 1) Shape Resonance (ν = 1)
Position (eV)
Width (meV)
Cross Section (m2)
Position (eV)
Width (eV)
Cross Section (m2)
HBr 041 <70 40 × 10−19 09 1 27 × 10−19
HCl 051 180 20 × 10−19 25 2 30 × 10−19
HF 051 <30 70 × 10−20 10 × 10−20
Note: Data for hydrogen chloride (HCl) and hydrogen fluoride (HF) are also given for comparison purposes
The potential energy diagram for the formation of Br− ion is shown in Figure 192Table 193 shows the electron impact data for HBr, and data for other hydrogen halides are included for comparison (Frost and McDowell, 1958)
Attachment cross sections for HBr, digitized from the measurements of Christophorou et al(1968) are shown in Table 194 and Figure 193
1 2 3 10-10 mro × Nuclear separation
En er
gy (V
)
H + Br-
H + Br
EA (Br) DE (HBr)
0.1 10.01 Energy (eV)
0.1
0.01
HBr
Attachment
Q a (1
m 2 )
0 1 2 3 4 5 6 7 Energy (eV)
Cr os
ss ec
tio n
(1 0-
2 ) 30
HBr Vibrational excitation (ν = 1)
Impact Data for Hydrogen Halides
Molecule/ Ion DE EA AP
Experimental
ReferenceOnset Peak
HBr/Br− 0396 039 Ziesel et al (1975)
011 028 Christophorou et al (1968)
375 354 021 010 021 Frost and McDowell (1958)
HCl/Cl− 0819 084 Ziesel et al (1975)
064 078 Christophorou et al (1968)
443 378 065 062 077 Frost and McDowell (1958)
084
HF/F− 583 363 220 188 40 Frost and McDowel (1958)
HI/I− ~0 ~0 Christophorou et al (1968)
306 324 –018 003 005 Frost and McDowell (1958)
Note:AP = appearance potential; DE = dissociation energy of the molecule; EA = electron affinity of the atom Energy in eV
TABLE 19.4 Dissociative Attachment Cross Sections
Energy (eV) Qa (10-20 m2) Energy (eV) Qa (10−20 m2)
008 0027 032 2565
010 0146 034 2329
012 0283 036 2056
014 0391 038 1824
016 0619 040 1643
018 1255 045 1151
020 1913 050 0787
022 2366 055 0537
024 2568 060 0429
026 2622 065 0377
028 2704 070 0319
030 2701 072 0288
Source:Adapted from Christophorou, LG, RNCompton, and HW Dickson, J. Chem. Phys., 48, 1949, 1968
Table 195 shows the attachment rate constants for HBr The attachment rate constants as a function of E/N and mean energy are shown in Figure 194 (Wang and Lee, 1988)
0.4
0 0 4 8 12
0.8
E/N (Td)
Mean electron energy (eV)
1.2
0.8
0.4
0 0 1 2 3 4
HBr-N2
HBr-Ar
HBr-Ar
HBr-N2
(b)
Attachment Rate CHBr
Temperature, K, (eV) Method
Rate Constant (×10−18 m3/s) Reference
1697 P/LP <10 Speck et al (2001) 1454 25
846 94
745 180
715 110
477 120a
Swarm 100 Wang and Lee (1988)
300 FA/LP ≤3 Smith and Adams (1987)
515 300
300 FA/LP 33 Adams et al (1986)
515 280
Swarm 100 Christophorou et al (1968)
Note: Temperature is thermal unless otherwise mentionedFA/LP = flowing afterglow/Langmuir probe; P/LP= plasma/Langmuir probe
a Possibly clusters of HBr molecules
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