Spectroscopy of atoms and molecules in liquid helium

Article Abstract:

Atoms and molecules are easily picked up by large liquid helium droplets; spectra are detected through use of either laser-induced fluorescence or beam depletion following absorption. Sensitivity is high. A variety of molecules ranging from a few atoms to large organic molecules have been embedded in He droplets and studied in the infrared region or the visible region. A new interdisciplinary branch of spectroscopic research has been born, with applications to molecular physics and low-temperature physics. Helium is the only known substance to remain liquid at normal pressures down to 0 K.

Germany, Atomic spectroscopy, Superfluidity, Chemistry, Physical and theoretical, Physical chemistry, Liquid helium

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Two-photon-induced fluorescence

Article Abstract:

Two-photon-induced fluorescence, the nonresonant two-photon electronic spectroscopy of polyatomic molecules, is proving useful. Three-photon studies have been carried out and two-photon-induced fluorescence anisotropy is being used for biological molecules. Pseudoparity rules provide a framework within which are found patterns in the excitation spectra of aromatic hydrocarbons and effects of substitution and vibrations. Quantum chemical predictions can be made about vibronic coupling and substituent effects on two-photon absorptivity and tensor properties of lone molecules.

Photons, Spectrum analysis, Spectroscopy, Electron spectroscopy, Fluorescence spectroscopy

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HCP-CPH isomerization: caught in the act

Article Abstract:

This article discusses energetic forces involved in the interconversion of polyatomic molecules from one mode to another. The vibrational spectrum of phosphaethyne is explained in the context of its potential energy surface, Schrodinger's equation, and the resonance Hamiltonian model.

International, Methods, Analysis, Testing, Quantum theory, Quantum mechanics, Isomerization, Molecular rotation, Hamiltonian systems, Vibrational spectra

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