Absolute photoionisation cross-sections of atomic and molecular fluorine at 584 Å

Abstract

Absolute photoionisation cross-sections for atomic and molecular fluorine at 584 Å are determined using the recently developed electron modulation spectroscopy method. The experiments yield angle-dependent (90°) cross-sections for the F 2 +( X 2Π g,i) ← F 2( X 1Σ + g) and F +( 3 P 2,1,0) ← F( 2 P) ionisations relative to the known absolute ground-state to ground-state HF +( X 2Π i) ← HF( X 1Σ +) photoionisation cross-section. Additional relative measurements of the transition probability to the accessible excited ionic states in F 2 and F allow the determination of total absolute photoionisation cross-sections at 90°. With the atomic asymmetry parameters available from an independent source, angle-integrated 584 Å photoionisation cross-sections for fluorine atoms can be determined.