Mass-resolved multiphoton ionization spectroscopy of jet-cooled Cl2. I. Bound-free-bound spectroscopy

Abstract

Spectroscopic constants, obtained using two-color optical double resonance via repulsive intermediate states, are presented for four ion-pair states of Cl 2 ; i.e., the E(0 g ϩ ), ␤͑1 g ͒, f (0 g ϩ ), and G(1 g ) states. One-color excitation, also via a repulsive intermediate state, has been used to further extend the vibrational data for the ␤͑1 g ͒ state. The same pumping scheme has been used to extend a vibrational progression in the ͓ 2 ⌸ 1/2 ͔ c 4s; 1 g Rydberg state. The absence of perturbations when the ͓ 2 ⌸ 1/2 ͔ c 4s; 1 g Rydberg and the ␤͑1 g ͒ ion-pair states cross, together with the key role played by the intermediate C(1 u ) state in accessing both singlet and triplet final states, are discussed in terms of the changes in spin-orbital coupling schemes that are required on bond stretching.

Mass-resolved multiphoton ionization spectroscopy of jet-cooled Cl2. II. The (2+1) REMPI spectrum between 76 000 and 90 000 cm−1

“…The ͑2ϩ1͒ REMPI spectrum between 71 000 and 77 000 cm Ϫ1 is dominated by a long vibrational progression in the ␤͑1 g ͒ ion-pair state. In an accompanying paper 6 we report that over this range there are no significant perturbations in the band positions and that any interaction with the 4s Rydberg states must be very weak.…”

“…The experimental arrangement is described in detail in Ref. 6. The frequency doubled output of the Coumarin dyes 307, 102, 47, and 120 covered the one-photon wavelength range 263-222.5 nm ͑i.e., equivalent to a two-photon energy range of 76 000-90 000 cm Ϫ1 ͒.…”

“…In the preceding paper, 6 we accounted for the absence of an interaction between the ␤ state and the 4s ⍀ϭ1 Rydberg states by pointing out that the preferred dominant configuration of the ␤ state, g 2 u 2 g 4 u 2 ͑2242͒, cannot mix with the ͓͑2430͔ns͒ configuration of the Rydberg states by a simple two-electron shift. The same argument should apply to the d states based on the same 2 ⌸ state of the core, but the first members of the progression, the 3d states, are observed to really have ⍀ϭ2, the 4d and 5d states may have to be reconsidered in this light.…”

“…4,5 In particular, a surprisingly long progression, with vЈϭ0-15, in the ͓ 2 ⌸ 1/2 ͔ c 4s; 1 g state was observed. In the accompanying paper we have reinvestigated this region, 6 using a ͑1ϩ1͒ double resonance, bound-free-bound, technique and conventional ͑2ϩ1͒ REMPI spectroscopy and have accessed many of the triplet gerade ion-pair states. The vibrational spacings in all of the observed progressions are essentially regular, indicating that there are no strong interactions in the energy region up to 78 000 cm Ϫ1 .…”

Heavy Rydberg behaviour in high vibrational levels of some ion-pair states of the halogens and inter-halogens

“…Higher i.p. vibrational levels of the β state of Cl 2 , correlating with Cl + ( 3 P 2 ), were accessed by two-photon excitation via a repulsive intermediate state by Al-Kahali et al, 22,23 which allows direct access to the i.p. levels rather than via doorway states.…”