Electronic spectroscopy and energy transfer pathways of matrix isolated iodine

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Abstract
Visible laser excitation (460–725 nm) of dilute rare gas/I2 (2000:1) matrices resulted in emission from the I2A 3Π(1u) state. Reanalysis of the A→X spectra provided revised molecular constants for matrix isolated I2. A state lifetimes of 70±20, 80±20, and 110±30 μs were observed in Ar, Kr, and Xe hosts, respectively. Excitation spectra for the A state closely followed the I2 continuum absorption spectrum, indicating that transfer from the B 3Π(0+u) and 1Π(1u) states was effective in populating I2(A). At dilution ratios of 600:1 or lower the I 2P1/2–2P3/2 transition was observed in conjunction with the A–X bands. Excitation studies showed that isolated I atoms, trapped during the deposition process, were excited by energy transfer from nearby I*2 molecules. A vibronic progression, similar to the A–X bands, but shifted to longer wavelengths, was noted in concentrated Rg/I2(300:1) matrices. This system, which was emitted with a lifetime of about 10 ms, most probably originated from perturbed I2 A′ 3Π(2u). Intermolecular energy transfer was observed in matrices that contained I2 codeposited with O2. Electronic excitation of I2 resulted in a long-lived emission from O2 a 1Δg. Matrices containing high concentrations of iodine also exhibited O2(a)→I(2P1/2) transfer.