Resonance Raman spectra are obtained when the wave number of the exciting radiation is close to, or coincident with, that of an electronic transition of the scattering species. Such spectra are usually characterized by a very large enhancement of the intensities of particular Raman bands, sometimes with the appearance of intense overtone and combination tone progressions. The technique provides detailed information about excited electronic states because it is only the vibrational modes associated with the chromophore that are resonance-Raman active. Additionally, the high sensitivity is such that compounds at concentrations as low as 10−6 mol/L may be detected, enabling resonance Raman spectroscopy to be used as an analytical tool and for the study of chromophores in molecules of biological interest.

Resonance Raman Spectroscopy, and Its Application to Inorganic Chemistry. New Analytical Methods (27)

Gas phase spectroscopic studies of copper trimer are reported. A band system in the 5430–5225 A region has been assigned to Cu3 and has been studied by resonant two‐photon ionization spectroscopy, spectroscopy by depletion through predissociation, and by radiation repopulation of excited vibrational states in a cold supersonic molecular beam. The spectrum fits well to a 2E″←2E′ transition of a D3h molecule with both states undergoing Jahn–Teller distortions. In this interpretation, the excited state is well described by a weak Jahn–Teller effect, stabilizing the molecule at a configuration in which one Cu–Cu bond length differs from the others by 0.03 A, with a Jahn–Teller stabilization energy of 9 cm−1. The ground electronic state corresponds to a deep Jahn–Teller situation with the lowest vibronic levels trapped in the distorted configuration. The spectra indicate the tunneling splitting of the lowest vibrational levels in the ground state is 12±7 cm−1. These assignments are based on measured vibrationa...

Spectroscopic studies of the jet-cooled copper trimer

8. Chemical Trapping 4200 C. Atom Activation 4200 1. Photolysis 4200 2. Discharge Methods 4201 3. Laser Ablation 4201 4. Chemical Methods 4201 5. Thermal Activation 4201 D. Apparatus 4202 1. Matrix Isolation 4202 2. Gas-Phase Studies 4202 III. Reaction Pathways 4202 A. Simple Addition Reactions 4204 B. Insertion 4205 C. Isomerization 4207 D. Decomposition 4208 IV. Comparison between Gas-Phase and Matrix Isolation Studies 4210

Reactions of Ground State and Electronically Excited Atoms of Main Group Elements: a Matrix Perspective

Raman spectra of matrix-isolated group IIIA dimers: Ga2, In2, Tl2

The HeI (584 A) high resolution photoelectron spectra of As+2, Sb+2, and Bi+2 have been obtained with a high temperature molecular beam source. A pure As2 beam was produced by evaporating Cu3As. Sb2 was generated as a mixture with the atoms and tetramers by evaporating the pure element, while Bi2 was generated as a mixture with only the atoms from the pure element. Vibrational structure was well resolved for the As+2 spectrum. Spectroscopic constants were derived and reported for the related ionic states. In addition, we have carried out relativistic complete active space self‐consistent field followed by multireference single + double configuration interaction calculations on these dimers both for the neutral ground states and the related ionic states. The agreements between the calculated and experimentally derived spectroscopic constants were fairly good, although the calculations tended to underestimate consistently the strength of the bonding in these heavy homonuclear diatomics.

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U. Engelhardt

Papers

Matrix Raman studies of Bin(n ⩾ 2) molecules