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    State resolved rotational relaxation of CO in the free jet expansion of He–CO mixtures

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    We describe an infrared molecular beam spectrometer which uses a semiconductor diode laser and has been used to study the rotational relaxation of CO molecules in the free jet expansion of pure CO and a 90% He-10% CO mixture. The data for the mixture are analyzed by means of a kinematical method based on the use of the master equation and empirically scaled state to state rate constants. Information of the He-CO rotationally inelastic rate constants are obtained. The possibility of using free jet expansion to study rotational inelastic collisions is discussed

    Infrared Spectroscopy of Supersonic Molecular Beams with Tunable Diode Lasers

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    Bolometric detection of infrared spectra obtained shining the output of a tunable IR laser on a supersonic molecular beam has been used to study the rotational distribution of carbon monoxide in free jets

    Molecular beam diagnostics by means of fast superconducting bolometer and pulsed infrared laser

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    The laser-bolometric infrared spectroscopy is an efficient method for measuring the internal energy distributions of molecular beams. Additional informations about the kinetic energy distribution of molecules in a selected internal state can be obtained from time resolved experiments. A fast superconducting bolometer and a pulsed infrared CO2 laser have been used for testing the use of this technique as a universal tool for molecular beam diagnostics. Experimental results are presented and analyzed for pure SF6 and helium seeded with 5% SF6 beams. The efficiency of fast superconducting bolometers, used for molecular beam time-of-flight measurements, is discussed. A comparison is made between time resolved laser-bolometric technique and alternative molecular beam diagnostic methods

    Infrared multiple-photon excitation of sulfur hexafluoride in a molecular beam

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    The infrared multiple photon excitation of SFg in a supersonic molecular beam has been investigated by means of the laser-bolometric technique. In this experiment molecules are irradiated below dissociation threshold in a true collisionless regime. The absorbed energy is detected by means of a fast superconducting bolometer. The molecular beam is obtained by expanding pure SF6 and SF6 seeded in helium or argon at different pressures. The multiple photon excitation spectra are very sensitive to the molecular beam conditions. Spectra become narrower as the pressure is increased. This effect has been attributed mainly to the rotational cooling which occurs during beam formation
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