$T_{2}$ FOR THE J = 2-0 TRANSITION OF OCS

$^{1}$H. Hatanaka, T. Tereo, and T. Hashi, J. Phys. Soc. Japan 39, 835 (1975). $^{2}$S. L. Coy, Molecular Spectroscopy Symposium, Columbus, Ohio, June 1977. Paper FD5. ""Author Institution: Department of Chemistry, Harvard UniversityThe coherent polarization relaxation time, $T_{2}$, for the $J = 2-0$ transition of OCS is measured by employing multi-pulse techniques previously used in $NMR^{1}$ Traditional methods of measuring $T_{2}$ are not applicable to this transition because direct absorption or emission for a $\Delta J= 2$ transition is forbidden by dipole selection rules. The pulse train used has 3 pulses. The (J,M) = (1,0) - (2,0) transition is Stark switched into resonance with a K-Band source in order to create a $\Pi/2$ pulse and, therefore, coherence between these two levels. Then, a $\Pi$ pulse at the $J = 1-0$ transition frequency $(\nu_{10})$ juxtaposes the 0 and 1 level populations, moving the coherence to the 0 and 2 levels. After a time, $\tau$, another $\Pi(\nu_{10})$ pulse shifts the coherence back to the 1 and 2 levels where the subsequent transient emission is recorded. Variation of $\tau$ allows the measurement of $T_{2}$ for the J = 2-0 transition. A 3-level analog to the Feynman, Vernon, Hellwarth representation of the Bloch equations is used to mathematically describe this pulse train. The results are interpreted according to traditional Anderson linewidth theory. The velocity dependent $T_{2}$ is found to be very nearly the same as those found for the J = 1-0 and J = 2-1 $transitions^{2}