Theory of muon spin relaxation of gaseous C2H4Mu.

A theoretical study of the muon spin relaxation of the gaseous muonated ethyl radical C{sub 2}H{sub 4}Mu is expanded in this paper to include both longitudinal and transverse signals. This study is based upon an operator expansion of the spin-density operator for the radical with its time dependence described by the linearized quantum Boltzmann equation. Relaxation is due to collisions which reorient the radical{close_quote}s rotational angular momentum while effects on the muon{close_quote}s spin are due to couplings between the muon{close_quote}s spin, the radical{close_quote}s free-electron spin, and the radical{close_quote}s rotational angular momentum. The coefficients of the radical{close_quote}s spin Hamiltonian and the collisional lifetimes (cross sections) are used as fitting parameters to describe the transverse signals. A fit to the transverse data by itself and a global fit to both the transverse and longitudinal data are obtained with good accuracy. {copyright} {ital 1996 The American Physical Society.}