Improved spectroscopic constants for I2 D 1Σu+

The D-X transition of I2 can be used to observe populations in vibrationally excited levels of I2(X). Levels in the range 20 ⩽ ν″ ⩽ 50 are sensitively detected by exciting transitions that terminate on I2(D) ν′ ⩽ 40. In the present work, spectroscopic studies of the lower vibrational levels of I2(D) were performed to facilitate use of the D-X transition for monitoring excited I2(X). New molecular constants for the D state are reported.