Multiphoton ionization/dissociation dynamics of formyl fluoride by velocity mapping ion imaging

Abstract

The dissociation dynamics of HFCO⁺ ion has been studied using the velocity map ion imaging technique. The HFCO⁺ ion is prepared by one-photon resonant three-photon ionization in the region of 43100–43860 cm⁻¹ excitation energy. The HFCO⁺ ions, produced by multiphoton ionization, have sufficient internal energy to dissociate into the F and HCO⁺ fragments without further absorption of another photon. Images of HCO⁺ have been recorded at various excitation energies. It is noticed that the angular distributions of HCO⁺ change dramatically from parallel distribution to perpendicular distribution and then back to parallel distribution in a very narrow excitation energy region of 43 473–43 500 cm⁻¹. Analysis of anisotropy parameters of β_n (n = 2, 4 and 6) reveals that the electronic states in the three-photon excitation of HFCO are mainly: HFCO(X¹A′) → HFCO(A¹A″) → HFCO(A′) → HFCO⁺(A²A″;B²A′). The purely perpendicular resonant transitions are likely responsible for the perpendicular angular distribution of the HCO⁺ ion fragment.