Energy transfer in mercury vapour following laser excitation of the 71S0 state by two-photon absorption

After excitation of the 71S0 mercury state by two photon absorption of a laser radiation at 313 nm the time integrated intensities of the 407.8 (I0) and 404.7 nm (I1) lines emitted from the 71S0 and 73S1 states were determined as functions of the pump laser intensity, I, and mercury pressure. At high pump laser intensities I0 and I1 do not follow anymore a quadratic law in I, I0 weakens to In 2. The time evolutions of the populations of these 71S0, 73S1 states and of the 61P1, 63P0,1,2 states were determined. The set of experimental results is well reproduced by introducing collisions of two Hg(6P) atoms as well as two Hg(71S0) collisions. Effects of these collisions are discussed.