Lineshape and temperature dependence of the nuclear quadrupole resonance of ¹⁴N2 in β-quinone clathrate

Authors:

• A.A.V Gibson,
• Roman Wacław Goc,
• T.A Scott

Abstract

Nuclear quadrupole resonance of ¹⁴N₂ molecules entrapped in β hydroquinone clathrate has been studied using Fourier transform spectroscopy. The spectrum at 4.2 K spans the frequency range 3.577 to 3.596 MHz and consists of three well-solved major components, each showing partially resolved fine structure. A consistent interpretation of intensities and frequencies is given by postulating that an N₂ molecule introduced into a clathrate cavity produces a slight lattice distortion extending to nearest-neighbor cavities arrayed along the crystallographic c axis, thereby affecting the electric field gradient. A one-to-one correlation is established among the three major components of the spectrum and the possible configurations for occupancy of nearest-neighbor cavities. Fine structure of the low- and high-frequency components is due to intramolecular dipolar interaction, whereas the middle component additionally exhibits a Stark splitting due to an asymmetric cavity environment. From the temperature dependence of the resonance frequency the molecular libration frequency in the cavity is deduced to be 50.7 cm^-1 at 0 K, the zero-point rms amplitude is 11.3°, and the static resonance frequency is 4.025 MHz. The libration frequency decreases by about 4% on warming to 80 K. © 1976.