Theoretical and experimental studies of the isotope effects for He–CO2 and Ne–CO2 complexes

Abstract

In this work, we have studied the isotope effects for the He–CO2 and Ne–CO2 complexes by means of theoretical calculations and experimental measurements, which were carried out using a distributed quantum cascade laser to probe a pulsed supersonic jet expansion. Firstly, infrared spectra have been recorded for the He/Ne–12C18O2 complexes. Spectroscopic parameters including band origin ν0, rotational constants A, B, C, and centrifugal distortion constants ΔJK were obtained by fitting a Watson A-reduced Hamiltonian with 13 assigned rovibrational transitions for He–12C18O2. For Ne–12C18O2, the observed spectrum produces a set of spectroscopic parameters including the band origin, rotational constants and all the quartic centrifugal distortion constants with more than 100 rovibrational transitions (40 new transitions). Secondly, we have calculated the rovibrational energy levels, vibrational shifts, and rotational constants for the He/Ne–CO2 complexes based on potential energy surfaces (PESs) and bound state calculations for ground and vibrationally excited states. The obtained results show that the spectroscopic characteristics (vibrational shifts and rotational constants) for Ne–CO2 are analogous to those of Ar–CO2, while those for He–CO2 show some differences especially for the rotational constants. Finally, according to the available experimental data and our theoretical calculations, infrared spectra were predicted for six isotopologues with C2v symmetry of Ne–CO2 complex.