SPECTROSCOPY OF I2 AT DISSOCIATION LIMIT

The spectroscopic analysis of the B 3Π0u+ state of I2 has been extended to both longer and shorter wavelengths. New assignments in the 6-3, 7-3, 8-4, 9-4, 10-5, 43-0, and 49-1 bands are reported. Absorption line coincidences with emission lines at 6328.17 Å (Ne I), 5145.36 Å (Ar II), and 5085.82 Å (Cd I) are identified. A revised best set of vibrational and rotational constants is given. The last discrete line observable in the spectrum falls at 4990.59 Å, some 24 cm-1 short of the true dissociation limit. This is attributed to small Franck-Condon factors for those levels within 24 cm-1 of the limit. The molecular potential curve has a -C R5 from for R > 4.5 A ̊, and this is attributed to a quadrupole exchange interaction. The transition quadrupole moment derived on this basis is within a factor of two of the calculated value. On the basis of this potential, it is estimated that the B state of I2 has 93 ± 2 bound vibrational levels. © 1969.