Internal rotation, Stark effect, and rotational magnetic moments in CH3CD3

Abstract

Ethane-1,1,1-d3 has been studied by the electric-resonance molecular-beam method. By anticrossing techniques, the zero-field energy differences for J = 1 and 2 have been measured corresponding to the normally forbidden selection rules (J ↔ J), [Formula: see text], and [Formula: see text]. From these splittings, three splitting ratio measurements, and four existing R-branch microwave frequencies, determinations were made of the moment of inertia of the CH3-top Iα = 3.1549(12) amu Å2 and of the effective height of the threefold barrier to internal rotation V3 = 1004.13(21) cm−1, as well as of B and several distortion constants. From the current CH3CD3 value of V3 together with previous values for asymmetrically deuterated forms of ethane, it has been shown that the change of V3 with deuteration is −3.05(13) cm−1 per deuteron. By conventional beam methods, the Stark and Zeeman effects have been studied. The Stark measurements have been analysed in terms of the anisotropy [Formula: see text] in the polarizability and the effective dipole moment for the matrix elements diagonal in J, namely μQ = μ0 + μJJ(J + 1) + μKK2. It has been found that μ0 = 0.0108617(5) D, μJ = 0.809(53) μD, μK = −2.06(10) μD, and [Formula: see text] = 0.672(27) × 10−24 cm3. The two molecular g factors have been measured, [Formula: see text] and [Formula: see text], and the anisotropy [Formula: see text] magnetic susceptibility has been evaluated.