RELAXATION OF MERCURY METASTABLE 6-P-3(0) ATOMS

In a mercury-nitrogen mixture illuminated with resonant light pulses at wavelength 253. 7 nm, metastable Hg(6 **3P//0) atoms are produced according to the process: Hg(6 **3P//1) plus N//2(X**1 SIGMA //g** plus , v equals 0) yields Hg(6 **3P//0) plus N//2(X**1 SIGMA //g**+30,v equals 1). It is observed that the decay of the metastable atoms concentration in the post-excitation depends upon the value of the light flux. This feature is partially explained by (i) a nonequilibrium situation for nitrogen molecules in the v equals 1 vibrational level (ii) inelastic collisions Hg(6 **3P//0 ) plus Hg(6 **3P//0) yields Hg(6 **1S//0) plus Hg*, where Hg* is a highly excited mercury atom. Excitation cross-sections for the 8 **1S//0, 8 **3S//1, 6 **1D//2, 6 **3D//2 and 6 **3D//3 levels have been measured and are respectively 15,9,12,4,10 and 6 A**2.