Photoelectron imaging spectroscopy for (2+1) resonance-enhanced multiphoton ionization of atomic iodine produced from A-band photolysis of CH3I

Abstract

Photoelectron imaging spectroscopy has been applied to study on two-photon resonant third photon ionization of two states of atomic iodine (5p5 P23/2 and P21/2) in the wavelength region 277–313 nm. The technique has yielded simultaneously both relative branching ratios to the four levels of I+(3P2, P30,1, D12 and S10) with 5p4 configuration and the angular distributions of outgoing photoelectrons. The product branching ratios reveal a strong propensity to populate particular levels in many cases. Several pathways have been documented for selective formation of I+(3P2), I+ (3P0,1) and I+(1D2) ions. In general, the final ion level distributions are dominated by the preservation of the ion core configuration of resonant excited state defined by the Jcl coupling scheme. Some deviations from this simple picture are discussed in terms of the configuration interaction of resonant states and the autoionization in the continuum. The photoelectron angular distributions are qualitatively similar, with a positive A2 anisotropy coefficient of 1.0–2.0 and negligible A4 in most cases, which suggests that higher-order Legendre terms are suppressed by the restriction of a maximum orbital angular momentum of ejected electron, 2.