Intensity analysis of overlapped discrete and continuous absorption by spectral simulation: the electronic transition moment for the B-X system in I2.

The spectrum of I(2) is examined anew in the wavelength region 520-640 nm, where discrete absorption in the B-X transition is prominent. The spectrum is recorded with high quantitative precision at moderate resolution (0.1 nm) and is analyzed by least-squares spectral simulation, yielding the B-X electronic transition strength ∣μ(e)∣(2) with unprecedented precision (<2% relative standard error) over most of the studied region. The analysis also yields directly new estimates of the continuous absorption in this region, which support previous assessments of the A ← X transition but lower the C((1)Π(u)) ← X transition strength by 25%. The new analysis method is applicable to any situation where the discrete spectrum can be simulated reliably.