Rate measurements for the reactions H + I₂→ HI + I and H + HI → H₂+ I by Lyman‐α‐fluorescence

Abstract

Rate constants for the reactions of hydrogen atoms with I2(k1) and HI(k2) have been determined in a discharge flow system using the detection of H‐atoms by Lyman‐α resonance fluorescence. Temperature dependent measurements in the range 250–420 K for H + I2 show an extremely weak variation with temperature k1,(H + I2) = (6.6 ± 3) 10−10 exp(‐20 K/T) cm3/molecule · s. which is equally well represented by the temperature independent expression k1, = (6 ± 2.5) 10−10 cm3/molecule · s. — From rate measurements for H + HI in the range 250–370 K the Arrhenius expression k2(H + HI) = (7.4 ± 2.0) 10−11 exp(‐290 K/T) cm3/molecule · s is obtained.

Kinetic Studies of the Reactions of Atomic Hydrogen with Iodoalkanes

“…13 At room temperature k 9 ≈ 2.4 × 10 -11 cm 3 molecule -1 s -1 . 18,19,20 Using the same k 2 /k 9 as Rebbert et al, the corrected k 2 is then 1.0 × 10 -11 cm 3 molecule -1 s -1 , close to the present value. The same explanation accounts for much of the discrepancy between the value of k 3 given by Rebbert et al, 13 1.6 × 10 -13 cm 3 molecule -1 s -1 , and our own direct measurement (Table 5) which is 90 times higher.…”

Rate Constants for the Reactions I + OClO, I + ClO, Cl + I2, and Cl + IO and Heat of Formation of IO Radicals

“…The only previous study of reaction 5 14 provided an indirect determination of k 5 = (2.4 ± 1.0) × 10 -11 cm 3 molecule -1 s -1 at T = 298 K. The present value of k 5 , obtained by a more direct way, is about 1 order of magnitude higher than that of this earlier work . A higher value for k 5 is acceptable when compared with the rate constants measured for similar reactions of molecular iodine with other atoms: H + I 2 , k = 6.6 × 10 -10 exp(−20/ T ) cm 3 molecule -1 s -1 ; O + I 2 , k = 1.4 × 10 -10 exp((0 ± 250)/ T ) cm 3 molecule -1 s -1 ; F + I 2 , k = (4.3 ± 1.1) × 10 -10 cm 3 molecule -1 s -1 ( T = 298 K) …”

Kinetics of the reaction: H+HI?H2+I at 298 K and very low pressures

“…Reaction 1 has been studied for over 50 years mostly in connection with the classical study of the once presumed, bimolecular reaction of H ϩ I 2 2 [1,2,23]. Despite this, there have only been two direct experimental studies [4,6] in the neighborhood of (Table I) and these gave values of 298 K k (298 K) 1 differing by 55%. Other indirect measurements, usu- (Table I).…”