An experimental and theoretical determination of the electron affinity of the ethynyl radical, HC2⋅

Abstract

The cross section for electron photodetachment has been measured for the acetylide anion (HC2−) using an ion cyclotron resonance spectrometer in conjunction with a xenon arc lamp. Calculation of the photodetachment behavior near threshold and an estimate of the Franck–Condon factors for the anion→neutral transition allow us to determine EA (HC2⋅) = 2.94±0.10 eV. A theoretical determination using eighth-order perturbation theory gives an adiabatic electron affinity of 3.18±0.25 eV, in good agreement with the experimental result. The use of a thermochemical cycle with the experimental electron affinity and gas-phase acidity data gives a C–H bond dissociation energy in acetylene of 132±5 kcal/mol.

Photodissociation of acetylene at 193.3 nm

“…al. 8 have come up with a value for Do(C 2 H-H) of 132*5 kcal/mol by combining processes VIII, IX and X in a thernochemical cycle. This result is in good agreement with the present work although the uncertainty is still fairly large.…”

Concurrent primary and metastatic cutaneous head and neck squamous cell carcinoma: Analysis of prognostic factors

“…All these experimental and theoretical details confirmed that CH 3 S and CH 3 S 2 are the products of the photodissociation. In comparison with the CH 3 S3, 11–21 radical, much less known about CH 3 S 2 radical, mainly because of its low stability and spontaneously dissociates to form slow S 2 and CH 3 radical. In 1990, the CH 3 S 2 radical from CH 3 SSCH 3 , was first detected by Nourbakhsh et al4 using translational spectroscopy.…”

Correlated calculations of the electron affinity of HC2

“…At this level of calculation, it may be seen that the difference between the vertical and adiabatic EAS of HC, is very mild. Zero-point vibrational correction is known to be comparable or even less significant [3,8]. The thermodynamic and photodetachment energies are calculated to have only a minor difference.…”