ABSTRACT
Figure 231 shows the attachment cross sections for I2 in the low-energy regionAt 300 K the cross section measured is 39 × 10−20 m2 (see Biondi, 1958)
TABLE 23.1 Electron Affinities of Halogen Atoms and Molecules
Electron Affinity (eV)
Atom Molecule
Bromine 3364 255
Chlorine 3613 238
Fluorine 3401 308
Iodine 3059 255
TABLE 23.2 Vibrational States and Energies Vibrational State 0 1 2 3 4 5 Energy (meV) 133 399 665 931 1198 1463
Note: Energy for the fundamental mode is 266 meV
TABLE 23.3 Selected References for Data
Parameter Range: eV, (Td) Reference
Qa 0-2 (1-50) Brooks et al. (1979) Qa 01-03 Birtwistle and Modinos
(1978)
AP 0-8 Tam and Wong (1978) ka 004-027 Truby (1969) Qa 0-10 Biondi and Fox (1958) Qa 0039 Biondi (1958) AP 0-3 Fox (1958) AP 0-7 Buchdal (1941)
W, ε0-200 Healy (1938)
Note:AP = Attachment processes; ka = attachment rate; Qa = attachment cross section; W = drift velocity, ε = mean energy Bold font indicates experimental study
231 Selected References for Data 145 232 Attachment Process 145 233 Attachment Cross Section 145 234 Attachment Rate Constants 146 235 Attachment Coefficients 146 236 Transport Parameters 147 References147
Figure 232 shows the attachment rate constants as a function of temperature (see Truby, 1969)Thermal (004 eV) attachment rate constant for I2 is 18 × 10−16 m3/s increasing to 28 × 10−16 m3/s at 027 eV energy (Truby, 1969)
cients in N2 as buffer gas at number density 16 × 1022 m−3 (Brooks et al1979)The attachment coefficient increases with temperature in the range from 35°C to 90°CThe earlier results of Healy (1938) for I2 are also shown (Figure 234)
0.1
Q a (1
m 2 )
Attachment (I2)
Biondi and Fox Buchdal Healy
0.01 0.001 0.01 0.1
Energy (eV) 1 10
×10-16
3.0
2.5
2.0
At ta
ch m
en tr
at ec
on sta
nt (m
3 / s)
Iodine (I2) 1.5
1.0
0.8 250 330 410
Temperature (K) 490
I2
110°C
90°C
50°C
35°C
η/ N
(1 0-
2 )
2 105 E/N (Td)
I2
Cl2
Br2
η/N × 5
×3.11 × 10-21
η/N × 10
15 7545 E/N (Td)
At ta
ch m
en tc
oe ffi
cie nt
(η /N
,m 2 )
Peak Energy for Negative IFormation
Peak Energy (eV) Peak Cross Section (m2) Reference
005 Tam and Wong (1978)
09
25
0 Fox (1958)
32 × 10−19 Biondi and Fox (1958) 04 Buchdal (1941)
Experiments of Healy(1938) are the only available data for drift velocities and mean energies, as shown in Figures 235 and 236
I2
Cl2 Br2
0 12060 E/N (Td)
180 240
Dr ift
ve lo
cit y(
10 4 m
/s )
I2
Cl2
Br2
0 12060 E/N (Td)
180 240
En er
gy ra
tio (k
)
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