ANOMALIES OF PRESSURE BROADENING IN THE H-2 S-0(3) TRANSITION VERSUS PERTURBER CONCENTRATION

Inhomogeneous broadening in vibrational Q lines for H-2 broadened by h eavy rare gases due to speed-changing collisions was previously demons trated through the nonlinear behavior of the linewidths versus the con centration. In order to explore a possible inhomogeneous broadening (s imilar mechanism) for a pure rotational relaxation mechanism, the broa dening and line shift of the pure rotational quadrupole transition S-0 (3) of H-2 have been measured to high precision with a frequency stabi lized diode laser spectrometer. Foreign gas effects with helium and ar gon at various dilution ratios in H-2 have been investigated. A nonlin ear dependence of the broadening on the mixing ratio was detected in a pure rotational transition for the H-2-Ar mixture. This is the spectr al signature expected for an inhomogeneous broadening due to speed-cha nging collisions.