Rotationally resolved infrared spectrum of the Cl−–H2 anion complex

Abstract

The mid-infrared spectrum of the Cl37−–H2 anion complex has been measured over the 3990–4050 cm−1 range (H–H stretch region) using infrared vibrational predissociation spectroscopy. The spectrum features a well resolved Σ–Σ transition red shifted by 156 cm−1 from the free H2 molecule stretch. Analysis of the P and R branch line positions using a linear molecule energy level expression yields ν0=4004.77±0.08 cm−1, B″=0.853±0.002 cm−1, D″=(9.3±1.0)×10−5cm−1, B′=0.919±0.002 cm−1, and D′=(9.0±1.0)×10−5 cm−1. The Cl−–H2 complex appears to have a linear equilibrium structure, with a vibrationally averaged separation of 3.19 Å between the Cl− and the H2 center-of-mass. Vibrational excitation of the H–H stretch induces a 0.12 Å contraction in the intermolecular bond.

Infrared studies of ionic clusters: The influence of Yuan T. Lee

“…204 An extended infrared study into the 600-1800 cm −1 region has identified the shared proton vibration in the H 3 O 2 − cluster ion at 697 cm −1 and was confirmed by full-dimensional diffusion Monte Carlo calculations. 209 Rotationally resolved vibrational bands of H 2 in X − ·H 2 have been assigned and analyzed to yield vibrationally averaged distances ͑anion to midpoint of H-H bond͒ of 3.20, 3.46, and 3.85 Å for chloride, 210 bromide, 211 and iodide, 212 respectively. Vibrational spectra of I − ͑ROH͒ 1 Ar n , for methanol, ethanol, and isopropanol, were measured to explore the dependence of the ionic hydrogen bond OH stretching frequency on the number of attached argons.…”

Ab initio potential energy surface, infrared spectra, and dynamics of the ion-molecule complexes between Br− and H2, D2, and HD

“…As for neutral systems, high-resolution spectroscopy of weakly bound complexes provides a powerful tool for studying ion-molecule interactions. [3][4][5][6][7] Accurate ab initio potential energy surfaces ͑PESs͒ were computed for the Cl − -H 2 ͑Refs. Among negatively charged systems, considerable attention has been paid to halogen atomic anions X − interacting with simple molecular ligands, particularly hydrogen and its isotopomers.…”

“…8-10͒ and Br − -H 2 ͑Ref. [3][4][5][6] The strong interaction anisotropy also influences the predissociation mechanism of the vibrationally excited complexes, which proceeds by resonant vibrational-to-rotational energy transfer. [7][8][9] It is worth adding that these studies have a bearing on the interpretation of the Cl − -H 2 /D 2 photoelectron spectra, [11][12][13] which help us characterize the dynamics of the fundamental neutral Cl+ H 2 reaction.…”

Photoelectron spectroscopy of the Cl−…H2∕D2 anions: A model beyond the rotationless and Franck–Condon approximations

“…51,52 However, it contains the effective temperature as a single adjustable parameter. Assumption of equilibrium may not be valid for the anion complexes in the beam: Indeed, remarkable deviations were noted in the rotationally resolved infrared spectra of the X − ...H 2 / D 2 complexes.…”