Determination of the 63P1→63P0 Transition Rate of Hg in CO and NO by a Modulation Technique

In order to determine the branching ratio for Hg(63P1) deactivation to the 63P0 and 61S0 states in CO or NO, a modulation technique was utilized. The intensity of 253.7-nm radiation was modulated at a frequency in the range from 0.1 to 20 kHz, and the resulting a.c. component of the Hg(63P1 or 63P0) concentration was measured by monitoring the absorption of the 435.8- or the 404.7-nm emission line from an Hg discharge lamp. The lower detection limit of excited Hg atoms was 107 cm−3 in this experimental method. On the basis of the Hg(63P0) concentration relative to that of Hg(63P1) in an Ar+CO or NO mixture including information on the phase delay, the 63P1→63P0 transition rate could be determined; the 63P1→63P0 cross section was found to be 22.4 Å2 for CO and 7.1 Å2 for NO and the 63P0→61S0 cross section to be 1.80 Å2 for CO and 37 Å2 for NO at room temperature.