Absolute Integrated Band Strength and Magnetic Dipole Transition Moments in the 2P3/2 → 2P1/2 Fine Structure (with Hyperfine Structure) Transition of the Iodine Atom: Experiment and Theory

Abstract

AbstractPrevious experimental and theoretical results on the strength of the important fine structure transition in the Iodine atom scatter over a very wide range, indicating great uncertainty. We have therefore carried out new theoretical calculations and experiments to reinvestigate the transition probability between the fine structure levels 2P3/2 and 2P1/2 in the electronic ground configuration of atomic iodine. In the experiments a tunable, narrow band width, near‐IR laser was used to measure the iodine absorption spectrum with sub‐Doppler resolution. The I‐atoms in the 2P3/2 ground state are produced either in a I2 = 2I equilibriums at elevated temperatures or from IR‐multiphoton dissociation of CF3I, CF3CHFI or C6F5I. The two different experimental methods to produce I‐atoms in the ground state allow for a careful check on possible systematic errors. In the experiments an integrated absorption cross section of Gexp = ∫ σ(v) dln v = (1050±250) fm2 was determined, corresponding to a radiative lifetime of 140 ms for spontaneous emission from the upper level. We have in addition carried out nonrelativistic MCHF calculations and relativistic Dirac‐Fock calculations on this transition. The results of the MCHF calculations (1200 fm2) agree well with experiment and a crude estimate from a simple LS coupling model.