Infrared laser spectroscopy of the nu band of CH2--CH37Cl

Abstract

The infrared spectrum of CH₂=CH³⁷Cl has been investigated in the υ₅ band region around 1370 cm^-1, at Doppler-limited resolution, using a tunable diode laser spectrometer. This vibration of symmetry species A′ yields an a/b hybrid band exhibiting patterns characteristic of molecules approaching the prolate symmetric top limit. The J fine structure was resolved in most of the ^(P,R)QK clusters and the rovibrational analysis in the P, Q and R branches led to the assignment of about 800 transitions with J ⩽ 49 and K_a ⩽ 11. The band is affected by different Coriolis-type resonances with the nearby states υ₈ + υ₁₂ and υ₉ + υ₁₀. Using the Watson's A-reduction Hamiltonian in the I^r representation, a least-squares fit of about 650 transitions free of major resonance contribution provided a set of effective molecular constants for the v ₅ = 1 state of CH₂=CH³⁷Cl. From spectral simulation the |Δµ _a /Δµ _b | dipole moment ratio was estimated to be 0·74 ± 0·08.