Knowledge Bank

A new steady-state lineshape function has been derived for collision-broadened transitions between spatially degenerate levels under conditions of partial saturation by an applied plane-polarized microwave fields. The new function, which is in the form of a continued fraction, is a steady-state solutions of the equations obtained after spherical tensor transformation of the usual equations (J.M basis) for the time development of the density matrix for a two-level system with spatial M degeneracy. Derivation of the new equation was motivated by a comparison of $qT1$/$T2$ $values1$ obtained by reanalysis of data taken at several sample pressures for transitions in pure $\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}NH3$ and in dilute mixtures of $\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}NH3$ in $H2$. The values of qT/$\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}$/$T2$ showed a considerably greater pressure dependence than previously obtained $(T1/T2)0$ $values,2$ and the reasons for and implications of this difference will be discussed in terms of the new lineshape function.