Spectroscopy of metastable species in a free-jet expansion: The D′←A′ transition of I2

Abstract
The A’2u 3Π state of I2 is observed in a free‐jet expansion of I2 in Ar, where it is prepared by ArF laser irradiation. Laser excitation spectra are recorded for 37 bands in the υ’←0‘ progression of the D’2g(3P2)←A’ transition. The spectra display rotational temperatures of ∼5 K. At the 0.08 cm−1 resolution of the probe laser, rotational congestion near the band origins necessitates analysis by a nonlinear least‐squares contour simulation method. Subsequent correlated fits of the band‐by‐band results are combined with other results to produce global constants valid for υ’=0–86, υ‘=0–32.