Abstract

The results were compared of experiments with a pulsed dye laser scanned between 5820 and 5920 Å or 6200 and 6700 Å for Na₂in a cross oven monitored by a PMT (with a UV filter) and a 0.5-m grating monochromator. The energy pooling process was observed around each of the D lines of Na with an excitation linewidth of ~1 Å (5 times wider than the others). The fluorescence energy was distributed mostly in the D lines, a few percent in the red band, more than 1 order of magnitude weaker in the 4300 Å diffuse band and very weak signals in the green region. This means that the process starting from the atomic first resonant transition could not efficiently populate high-lying states in Na₂. In contrast, many molecular two-photon excitations between 6200 and 6700 Å with a linewidth of 0.2 Å contributed as much as 50% of the fluorescence energy out of the A-X red band. While one part of these excitations distributed their fluorescence over three or four electronic spectral bands centered at 3200, 3600, 4350, and 5200 Å with bandwidths of a few angstroms, other excitations were found to concentrate 30% of their fluorescence energy in the 4300-Å diffuse band.

© 1986 Optical Society of America