(2+1) resonantly enhanced multiphoton ionization spectra of jet-cooled Kr2 between ≊91 800 and 94 100 cm−1 have been recorded. Single isotopomer excitation spectra were obtained using time-of-flight mass detection. Vibronic structure for several Rydberg ← ground state transitions involving excited gerade states which dissociate to Kr+Kr* (4p55p) have been unambiguously analyzed for the first time, and molecular constants derived. Bond lengths were estimated from Franck–Condon calculations. These results compare favorably with recent ab initio calculations. Excited state predissociation effects were inferred from excitation spectra obtained by monitoring atomic daughter fragment ions in TOF.

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Articles you may be interested inMassresolved multiphoton ionization spectroscopy of jetcooled Cl2. II. The (2+1) REMPI spectrum between 76 000 and 90000 cm−1 New ͑2ϩ1͒ resonantly enhanced multiphoton ionization ͑REMPI͒ spectra of ArKr in the region of Kr*(5p) and Ar*(4s) between Ϸ92378.8 and 94250.7 cm Ϫ1 are presented. A time-of-flight ͑TOF͒ mass spectrometer was used to obtain single isotopomer data. Four band systems, two previously observed by Dehmer and Pratt ͓J. Chem. Phys. 88, 4139 ͑1988͔͒, and two new ones, have been vibrationally analyzed. Excited state bond lengths have been found from Franck-Condon factor calculations while electronic symmetries were assigned from REMPI spectra recorded with circularly polarized light. Our excited state symmetry assignments differ from those recently proposed by Heck et al. ͓J. Phys. Chem. 99, 17700 ͑1995͔͒. The unusual vibrational band intensity distributions observed for some of the electronic systems are rationalized qualitatively in terms of interstate avoided crossings.

Jet-cooled, laser induced phosphorescence (LIP) excitation spectra of thioacetaldehyde (CH3CHS, CH3CDS, CD3CHS, and CD3CDS) have been observed in the 15 800–17 300 cm−1 region in a continuous pyrolysis jet. The responsible electronic transition, T1 ← S0, ã 3A″← X̃ 1A′, results from an n→π* electron promotion and gives rise to a pattern of vibronic bands that can be attributed to activity of the methyl torsion and the aldehyde hydrogen out-of-plane wagging modes. Potential and kinetic energy surfaces were mapped out for the aldehyde wagging (α) and the torsional (Θ) internal coordinates by using 6–31G* Hartree–Fock calculations in which the structural parameters were fully relaxed. The potential and kinetic energy data points were fitted to double Fourier expansions in α and Θ and were incorporated into a two-dimensional Hamiltonian operator. The spectrum was simulated from the transition energies and the Franck–Condon factors and was compared to the observed jet cooled LIP spectra. It was concluded that while the RHF procedure gives a good description to the ground state dynamics, the triplet state surface generated by the UHF method is too bumpy and undulating.

New mass-resolved two-photon spectra of NeXe involving molecular Rydberg states that dissociate to Ne+Xe*(6p) have been recorded using the combined techniques of (2+1) resonance enhanced multiphoton ionization and time-of-flight mass spectrometry. Excited state symmetries were deduced from separate spectra recorded with linearly and circularly polarized light. Vibronic analyses show that most of the excited states in this spectral region are essentially repulsive except for shallow minima whose electronic origins lie above their asymptotic dissociation limits. The magnitude of the potential humps for the excited states have been estimated. These results are rationalized in terms of an excited state bonding scheme that is dominated predominately by the interplay between repulsive exchange interactions and attractive long-range forces.