Optical detection of chlorine NQR of p-dichlorobenzene in a mixed single crystal in a magnetic field

Abstract

By a combined optical and microwave pumping cycle, chlorine NQR transitions could be observed for a dilute mixed single crystal of p-dichlorobenzene ( p-DCB) in p-dibromobenzene ( p-DBB). From the line splittings in the NQR spectrum of the singlet ground state of p-DCB for an orientation of the external magnetic field B o parallel to one of the in-plane fine structure axes, a considerable deviation (Δθ = 12°, Δφ = 20°) of this axis from a direction expected for an undistorted triplet-state molecule can be calculated. In addition, a lower limit of the electric field-gradient asymmetry parameter (η > 0.06) for singlet state p-DCB in the p-DBB matrix at 1.2 K is established.