The A–X system of the I2 molecule

Abstract

The A3Π1u–X1Σg+ system of the I2 molecule, lying in the 9600–8000 Å region, has been photographed in absorption under conditions of high dispersion. The band origins and B′ values of 18 bands in the lengthy progressions based on ν″ = 4 and 5 have been determined. By assuming that the potential curve of the A state is a Morse curve, an estimate of the vibrational numbering of this state has been made. Based on this numbering estimates of important constants of the A3Π1u state have been achieved: viz., Te = 11 059 cm−1, De = 1488 cm−1, ωe = 95.9 cm−1, Be = 0.02817 cm−1, and re = 3.071 Å. A comparison between the A state and the lower state of the ultraviolet laser transitions of the I2 molecule, based on the values of the constants De, ωe, xeωe, and yeωe, shows that the A state cannot be the lower state of the laser transitions.