HXeI and HXeH in Ar, Kr, and Xe matrices: Experiment and simulation

Abstract

Experimental and theoretical studies of HXeI and HXeH molecules in Ar, Kr, and Xe matrices are presented. HXeI exhibits the H–Xe stretching bands at 1238.0 and 1239.0 cm−1 in Ar and Kr matrices, respectively, that are blue-shifted from the HXeI band observed in a Xe matrix (1193 cm−1) by 45 and 46 cm−1. These shifts are larger than those observed previously for HXeCl (27 and 16 cm−1) and HXeBr (37 and 23 cm−1); thus, the matrix effect is stronger for less stable molecules. The results for HXeI are qualitatively different from all previous results on noble-gas hydrides with respect to the frequency order between Ar and Kr matrices. For previously studied HXeCl, HXeBr, and HXeCCH, the H–Xe stretching frequency is reliably (by >10 cm−1) higher in an Ar matrix than in a Kr matrix. In contrast, the H–Xe stretching frequency of HXeI in an Ar matrix is slightly lower than that in a Kr matrix. HXeH absorbs in Ar and Kr matrices at 1203.2 and 1192.1 cm−1 (the stronger band for a Kr matrix), respectively. These bands are blue-shifted from the stronger band of HXeH in a Xe matrix (1166 cm−1) by 37 and 26 cm−1, and this frequency order is the same as observed for HXeCl, HXeBr, and HXeCCH but different from HXeI. The present hybrid quantum-classical simulations successfully describe the main experimental findings. For HXeI in the 〈110〉 (double substitution) site, the order of the H–Xe stretching frequencies (ν(Xe) < ν(Ar) < ν(Kr)) is in accord with the experimental observations, and also the frequency shifts in Ar and Kr matrices from a Xe matrix are well predicted (30 and 34 cm−1). Both in the theory and experiment, the order of the H–Xe stretching frequencies differs from the case of HXeCl, which suggests the adequate theoretical description of the matrix effect. For HXeH in the 〈100〉 (single substitution) site, the order of the frequencies is ν(Xe) < ν(Kr) < ν(Ar), which also agrees with the experiments. The calculated frequency shifts for HXeH in Ar and Kr matrices with respect to a Xe matrix (36 and 23 cm−1) are in a good agreement with the experiments. The present calculations predict an increase of the H–Xe stretching frequencies in the noble-gas matrices with respect to vacuum.

Thermal decomposition of the HXeCl···H2O complex in solid xenon: Experimental characterization of the two-body decomposition channel

“…However, the energetic stabilization or destabilization of HNgY molecule by a matrix is still unclear; there are a few experimental studies on the environmental effects on HNgY molecules [14][15][16]. Khriachtchev et al studied relative stabilities of HXeOH and HXeOXeH in a Xe matrix at 55 K and found that HXeOXeH is more stable than HXeOH [17].…”

“…The discrepancy might originate from the fact that theoretical calculations are done for species in vacuum whereas the experiments are done for the species in the solid phase. There are some attempts to model the environmental effect on HNgY; e.g., on the H-Ng stretching frequencies of HNgY in different matrices [15,[19][20][21][22][23]. Among these studies, the methodology developed by Nakayama and co-workers could reproduce the experimentally observed order of H-Ng stretching frequencies [15,19].…”

Matrix site effects on vibrational frequencies of HXeCCH, HXeBr, and HXeI: a hybrid quantum-classical simulation

“…The stress acting on HXeY would be an important factor affecting the vibrational shifts, which was also suggested by Kalinowski et al 19 We note in passing that the small stabilization energies in the Ne matrix (sometimes positive values) can be related to the rather structureless configurations of Ne atoms around HXeY. Also, as pointed out in the previous work, 31 it may be the reason for a failure to prepare HXeI in the Ne matrix experimentally. It is also interesting to note that the frequency shifts from the gas-phase values exhibit a trend Dn(HXeCCH) E Dn(HXeCl) o Dn(HXeBr) o Dn(HXeI) in the same Ng matrix environments.…”

“…Similar observations have been made for HXeCl and HXeI in our previous studies. 28,31 As shown above in the frequency analysis of HXeY-Ng, the H-Xe stretching frequency is strongly affected by Ng atoms that are close to the hydrogen atom. In this situation, a displacement of the Ng atom toward the hydrogen atom results in a blue shift because the potential energy curve is quite repulsive when the Ng atom is located closer to the hydrogen atom.…”

Matrix-isolation and computational study of the HKrCCH⋯HCCH complex

“…It is therefore most likely that the polarizable matrix enhances the charge separation in the molecule, blue-shiing the H-Ng stretching mode. This effect is predicted for a number of HNgY molecules by the polarized continuum model, 35 DFT calculations in noble-gas clusters, 36 and hybrid quantum-classical simulations, 37,38 although an opposite opinion has been derived from the MP4 method.…”