# DETERMINATION OF $T_{2}/T_{1}$ FOR $^{15}NH_{3}$ INVERSION TRANSITIONS BROADENED BY $H_{2}$

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 Title: DETERMINATION OF $T_{2}/T_{1}$ FOR $^{15}NH_{3}$ INVERSION TRANSITIONS BROADENED BY $H_{2}$ Creators: Amano, T.; Schwendeman, R. H. Issue Date: 1977 Publisher: Ohio State University Abstract: Precise measurement of power-broadened linewidths with a computer-controlled microwave spectrometer together with measurement of microwave power make it possible to determine the relaxation times $T_{1}$ and $T_{2}$. The method was previously shown to be effective by application to the measurement of the self-broadening of microwave lines of $OCS^{1}$ and $^{15}NH_{3}.^{2}$ The $^{15}NH_{3}$ gas was mixed with $H_{2}$ inside the sample cell. The spectra were taken at various mixing ratios that ranged from $38 (H_{2}:NH_{3})$ to 750 in order to examine the systematic change of $T_{2}/T_{1}$ values. The values for $T_{2}/T_{1}$ range from 1.01 for the (J = 1, K = 1) to 1.39 for the (J = 8, K = 7) transition, and are closer to one than the corresponding values for the self-broadened lines. This tendency may be explained by assuming that the ratio of the effectiveness of $\alpha$-type^{\prime\prime} collision-induced transitions ($\Delta J = \pm 1$) to that of $\beta$ -type^{\prime\prime} collision-induced transitions ($\Delta J = 0$) is greater for $H_{2}$ broadening than for self-broadening. This is especially true for lower J and K transitions, and is consistent with the observations in the four-level microwave-microwave double resonance experiment by Daly and $Oka.^{3}$^{\prime\prime} Description: $^{1}$ R. A. Creswell, S. R. Brown, and R. H. Schwendeman, J. Chem. Phys. 64, 1820 (1976). $^{2}$ T. Amano and R. H. Schwendeman, J. Chem. Phys. 65, 5133 (1976). $^{3}$ P. W. Daly and T. Oka, J. Chem. Phys. 53, 3272 (1970). This research was supported, in part, by the U.S. National Science Foundation. Author Institution: Department of Chemistry, Michigan State University URI: http://hdl.handle.net/1811/10273 Other Identifiers: 1977-TG-14