LASER FLUORESCENCE STATE SELECTED AND DETECTED MOLECULAR BEAM MAGNETIC RESONANCE IN $I_{2}$

1. Rosner, Holt, Gaily, PRL 35, 785, ’75. 2. Hackel, Casleton, Kukolich, Ezekiel, PRL 35, 568, ’75.Author Institution:Radio frequency transitions of the type $\Delta J = 0, \Delta F = \pm 1$ having linewidths of 5 to 15 KHz have been observed in $I_{2}$. The experiment is exactly analogous to, MBMR spectroscopy as introduced by Rabi and coworkers. However, state selection is accomplished by laser excitation out of the initial spectroscopic level using the $Ar^{+} 5145$ {\AA} coincidence in $I_{2}.^{1}$ Following the magnetic resonance region, the occurrence of a hyperfine transition is monitored with a second laser excitation and fluorescence detection. 30 transition within the J=13 and J=15 levels of v=0 $I_{2}$ have been observed. Detailed analysis of the J=13 data provide the following parameters: eqQ=-2452.58 MHz, S=1.58 KHz, C=3.16 KHz, J=3.66 KHz, B=1118.6 MHz. It is interesting to note that this radio frequency data yields a rotational constant as accurate as Fourier Transform spectroscopy. Using this ground state data, much more accurate electronic excited state properties have been obtained from the reanalysis of the precise optical $data.^{2}