Ground-state rotational spectrum and spectroscopic parameters of the gauche butane conformer

Abstract

The rotational spectrum of gauche butane, CH₃(CH₂)₂CH₃, has been investigated between 100 and 150 GHz, and vibronic-ground-state transitions have been assigned. In a few cases, multiplet splitting caused by internal tunnelling was observed. Most of the transitions appear as singlets which could be analyzed in terms of the standard rigid-rotor model including centrifugal perturbations up to sixth order. The electric dipole moment, oriented along the molecular b axis, was measured to be (0·0900 ± 0·0015) D.