Vibrational Feshbach resonances in near-threshold HOCO−photodetachment: A theoretical study

Abstract

The results of a theoretical study of HOCO − photodetachment are presented, with a view toward understanding the origin of two peaks observed by Lu and Continetti (Phys. Rev. Lett. 99, 113005 (2007)) in the photoelectron kinetic energy spectrum very close to threshold. It is shown that the peaks can be attributed to vibrational Feshbach resonances of dipole-bound trans-HOCO − , and not s-and p-wave shape resonances as previously assumed. Fixed-nuclei variational electron-HOCO scattering calculations are used to compute photodetachment cross sections and laboratory-frame photoelectron angular distributions. The calculations show a broad A ′′ (π*)-shape resonance several eV above threshold.

Spectroscopy and dynamics of the HOCO radical: insights into the OH + CO → H + CO2reaction

“…A theoretical study by Miyabe et al found no shape resonances at these energies, and instead suggested that the resonance is a Feshbach resonance supported by dipole-bound anion states. 106 Their calculations predicted cisand trans-HOCO to have large dipole moments; 1.86 and 2.84 Debye, respectively, at the MP2 level of theory using Dunning's triple-z Gaussian-orbital basis set supplemented with diffuse primitive Gaussian functions. 106 In more recent experiments, the characteristic two-photon signal was also observed at 775 nm using the EIBT, and furthermore observed over a range of photon energies from 1.60 to 1.77 eV.…”

“…106 Their calculations predicted cisand trans-HOCO to have large dipole moments; 1.86 and 2.84 Debye, respectively, at the MP2 level of theory using Dunning's triple-z Gaussian-orbital basis set supplemented with diffuse primitive Gaussian functions. 106 In more recent experiments, the characteristic two-photon signal was also observed at 775 nm using the EIBT, and furthermore observed over a range of photon energies from 1.60 to 1.77 eV. This confirms that the resonance(s) responsible for this effect must be broad, consistent with a dense manifold of dipole-bound states.…”

Electron Affinities, Well Depths, and Vibrational Spectroscopy of cis- and trans-HOCO

“…Photoelectron spectra near threshold (772 nm) revealed two peaks at low electron kinetic energy that were not conclusively assigned, as a broad background arising from internally excited anions prevented unambiguous resolution of the peaks . These features were recently suggested to arise from vibrational Feshbach resonances in dipole-bound states, though the potential for pure photodetachment was not ruled out …”

Photodetachment cross sections of theC2nH− (n=1–3)hydrocarbon-chain anions

“…The transition dipole moments obtained from the Kohn trial function have been shown to be variationally stable [23] and the method has been applied in past studies on the photoionization of diatomic molecules such as H 2 and CO [24,25]. The Kohn technique was also used to calculate the radiative electron attachment to the CN radical [13] and to study the photodetachment of HOCO − [26].…”