Rotational States of Methyl Radical Monitored by EPR Line Shape of Matrix-Isolated CH$_{3}$ in CO$_{2}$ and N$_{2}$O Solids

Abstract

Methyl radicals, CH$_{3}$, were trapped in matrices of solid CO$_{2}$ and N$_{2}$O by condensing the methyl along with the matrix constituents from the gas phase. The obtained EPR spectra were analyzed using EasySpin and/ or SimFonia simulation software and ab-initio computed quantum-chemistry parameters. We focus on two distinguished features of the spectra: the temperature-dependent linewidth anisotropy and the origin of the weak satellite doublets. The low-temperature spectral analysis of the satellites was based on the coupled representation of the three proton spins of CH$_{3}$ and a recently obtained parameterization of the spin Hamiltonian based on one nuclear quartet and two doublets within the D$_{3}$ group. These features were closely correlated to the state of rotation of the trapped radical.