Intermolecular Frequencies of N2o–kr and Symmetry Breaking of the N2o Bending Mode in the Presence of a Rare Gas

Abstract

Rotationally-resolved infrared spectra of N 2 O-Ar and N 2 O-Kr van der Waals clusters are studied in the region of the N 2 O ν 1 vibration (≈ 2224 cm −1 ) using a tunable Quantum Cascade laser source to probe a pulsed supersonic jet. The N 2 O-Kr ν 1 fundamental band is re-analyzed, together with previous ν 3 band data, using a unified scheme to fit the (small) observed Kr isotope splittings. This scheme is then transferred to analyze the bending combination band of N 2 O-Kr near 2257 cm −1 where isotope effects are much larger due to stretch-bend Coriolis interactions. As a result, N 2 O-Kr intermolecular bend (33.29 cm −1 ) and stretch (34.48 cm −1 ) frequencies are directly determined for the first time.We also report observation of weak spectra for both N 2 O-Ar and -Kr corresponding to the (ν 1 , ν 2 l2 , ν 3 ) = (1,1 1 ,0) ← (0,1 1 ,0) hot band of N 2 O, located around 2209.8cm −1 . In the presence of Argon/Krypton atom, the doubly-degenerate ν 2 bending mode of the N 2 O monomer splits into an in-plane and an out-of-plane mode. These two infrared bands are heavily linked by Coriolis interactions and their analysis yields the magnitude of the splitting of the bending modes which are significantly smaller than those observed in the analogous CO 2 -containing dimers a . The experimental results obtained here are valuable for testing the accuracy of theoretical calculation toward a better understanding of intermolecular interactions.