Ps. Monks et al., DISCHARGE FLOW-PHOTOIONIZATION MASS-SPECTROMETRIC STUDY OF HOI - PHOTOIONIZATION EFFICIENCY SPECTRUM AND IONIZATION-ENERGY, Journal of physical chemistry, 99(45), 1995, pp. 16566-16570
Photoionization efficiency (PIE) spectra of HOI were measured over the
wavelength range lambda = 115-130 nm and in the ionization threshold
region, lambda = 123-129 nm, using a discharge flow-photoionization ma
ss spectrometer apparatus coupled to a synchrotron radiation source. H
OI was generated, in situ but in varying amounts, by three separate re
actions: OH + I-2; OH + CF3I; O(P-3) + C2H5I. The PIE spectra displaye
d steplike behavior near threshold, and the HO-I stretching frequency
in the cation was determined to be 702 +/- 60 cm(-1). A value of (9.81
(1) +/- 0.02(0)) eV was obtained for the adiabatic ionization energy (
IE) of HOI from photoion thresholds, corresponding to the HOI+(X(2)A '
') <-- HOI(X(l)A') transition. Even though the present result appears
to be the first reported determination of IE(HOI), the experimental va
lue is compared to an estimated value previously derived via a trend a
nalysis and it is considered in terms of trends in the series IE(HOX),
where X = F, Cl, Br, and I. The branching ratio for [HOI]/[IO] in the
O(P-3) + C2H5I reaction was estimated to be about 8/1 at T = 298 K if
we assume that the photoionization efficiencies for HOI and IO are th
e same at 10.3 eV (lambda = 120 nm). Also, based on the value for IE(H
OI) derived in the present study, a value for IE(IO) approximate to 9.
66 +/- 0.10 eV has been predicted.