ABSTRACT
The potential energy diagram for the formation of I− ion is shown in Figure 221 (Klar et al, 2001)The significant feature is that the dissociation energy of the molecule is almost equal to the electron affinity of the iodine atom with a peak in the attachment cross section occurring at 0 eV
Table 222 shows the electron impact data at low energies for HIData for other halogen halides are also included for comparison
Attachment cross sections for the dissociative process are shown in Table 223 and Figure 222
221 Selected References for Data 141 222 Attachment Processes141 223 Attachment Cross Section141 224 Attachment Rates143 References143
TABLE 22.1 Selected References for Data on HBr
Parameter Range: eV, (Td), [K] Reference
ka, Qa 0-3 Klar et al. (2001) ka [300, 510] Smith and Adams (1987) ka [300, 510] Adams et al. (1986) ka, Qa 0-15, (0-2) Christophorou et al. (1968) AP 0-1 Frost and McDowell (1958)
Note:Bold font indicates experimental studyAP = attachment process; ka = attachment rate constant, Qa = attachment cross section
En er
gy (e
V)
Nuclear separation r0
HI
H + I-
H + I
D(HI) E(I)
Electron IData for H
Experimental
Molecule /Ion DE EA AP Onset Peak Reference
HI/I− ~0 ~0 Christophorou et al (1968)
306 324 −018 003 005 Frost and McDowell (1958) 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 McDowell (1958)
Note:AP = appearance potential; DE = dissociation energy of the molecule; EA = electron affinity of the atom Energy in eV
TABLE 22.3 Dissociative Attachment Cross Sections for HI
Klar et al. (2001) Christophorou et al. (1968)
Energy (meV) Qa (10−20 m2) Energy (meV) Qa (10−20 m2)
02 18,256 10 2254
10 5595 20 2231
20 3311 30 2115
30 2485 40 1974
40 1802 50 1859
50 1395 60 1737
60 1194 70 1543
70 1080 80 1474
80 974 90 1341
90 871 100 1212
100 779 120 9789
125 603 140 8286
150 487 160 7296
175 407 180 6222
200 354 200 5287
25 290 220 4784
30 244 240 4367
35 206 260 3879
40 174 280 3588
45 151 300 3372
50 133 320 3072
55 121 340 2687
60 113 360 2397
65 107 380 2111
70 102 400 1856
80 90 420 1712
90 79 440 1566
100 68 460 1386
110 61 480 1223
120 57 500 1113
10-1 10-3
10-2
10-1
Attachment (HI)
101 Energy (meV)
102 103 104
TABLE 22.3 (continued) Dissociative Attachment Cross Sections for HI
Klar et al. (2001) Christophorou et al. (1968)
Energy (meV) Qa (10−20 m2) Energy (meV) Qa (10−20 m2)
130 55 550 1064
140 54 600 915
150 52 650 704
160 47 700 641
170 40 800 316
— — 900 203
Figure 223 is a graphical presentation
D ea
ra te
co effi
cie nt
(1 0-
7 c m
)
0.01 0.1 Mean electron energy (eV)
10 I-/ HI
1000 Electron temperature (K)
10,000
Attachment Rate CHI
Temperature, K, (Td) Method
Rate Constant
(10−13 m3/s) Reference
LPA 30 Klar et al (2001)
300 FA/LP 30 Smith and Adams (1987)
300 FA/LP 35 Adams et al (1986)
510 35
(06) Swarm 186 Christophorou et al (1968)
Note: Temperature is thermal unless otherwise mentionedFA/LP = flowing afterglow/Langmuir probe; LPA = laser photoelectron attachment method
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