An experimental study of HF photodissociation: Spin–orbit branching ratio and infrared alignment

Abstract

Single rotational levels of HF ͑vϭ3͒ were prepared by using overtone excitation and these molecules were then photodissociated by ultraviolet ͑UV͒ radiation at 193.3 nm. Time-of-flight spectra of the hydrogen atom fragment provided the spin-orbit state distribution of the fluorine fragment. Changing the UV photolysis laser polarization confirmed an A 1 ⌸←X 1 ⌺ ϩ electronic transition in the photodissociation step. Photodissociation of HF at 121.6 nm is also reported. Infrared ͑IR͒ induced alignment of the diatom was studied by monitoring the IR laser polarization dependence of the H-atom product angular distribution. Depolarization due to hyperfine interaction was studied by using the R͑0͒ transition. Agreement with theory is excellent.

Spin–orbit branching in the photodissociation of HF and DF. I. A time-dependent wave packet study for excitation from v=0

“…However, there has been only one experimental investigation of the spin-orbit branching in HF. 32 The main reason for the lack of study is due to the experimental difficulties in dealing with HF; namely, its highly corrosive nature and an absorption that lies in the vacuum ultraviolet ͑VUV͒. [33][34][35] But while it is experimentally difficult to investigate, HF provides an ideal system to investigate theoretically.…”

Photodissociation of HCl at 193.3 nm: Spin–orbit branching ratio

“…This differs from uv photodissociation of HF in which both F* and F have 100% perpendicular character. 13 It seems that as the molecule gets larger, besides the dominant singlet-singlet ͑ A 1 ⌸←X 1 ⌺ ϩ , perpendicular͒ transition, a minor singlettriplet transition ͑a 3 ⌸ 0 ϩ← X 1 ⌺ ϩ , parallel͒ starts to become noticeable, to a small extent in HCl and to a much larger extent in HI.…”

“…[11][12][13] The apparatus has been described previously. 12,13 A pulsed HCl molecular beam was produced by expanding 1% HCl in Ar or 5% HCl in He at a total pressure of ϳ760 Torr.…”

Effects of asymptotic interactions on the photodissociation of HCl

“…1,2 This latter type of interactions has been the focus of numerous studies by Freed and co-workers on the direct dissociation of diatomic molecules such as Na 2 , 3 NaH, 4 and CH ϩ . 5 Photodissociation of hydrogen halides [6][7][8][9][10][11][12][13][14] is quite interesting, since the potential curves of the Born-Oppenheimer states correlating to the lowest electronic state of the halogen atom ( 2 P j , jϭ1/2, 3/2) are well known. Low-energy photodissociation of HCl ͑Refs.…”