Measurement of pressure broadening of the 2S-3S transition of $^{7}$Li by noble gases

Doppler-free two-photon spectroscopy offers a unique combination of advantages for line-broadening studies. The narrow lines make resolution of small changes in linewidth more easily observable, while the fact that entire velocity distribution is excited ensures that a thermal distribution at the temperature of the sample is being studied. We have employed this technique in studying line broadening of the 2s-3s state of $^{7}$Li by Ne, Ar, Kr, and Xe. Experimental broadening rates are modeled in the impact approximation using available ab initio potentials.