1,720,989 research outputs found
State resolved rotational relaxation of CO in the free jet expansion of He–CO mixtures
No full textWe 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
Study of collisionless infrared multiple-photon absorption of SF6 in a variable temperature molecular beam.
No full textStudio del processo di eccitazione multifotonica infrarossa di un fascio molecolare di SF6
No full textMolecular beam diagnostics by means of fast superconducting bolometer and pulsed infrared laser
No full textThe 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
No full textThe 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
Proposta dell`Unita` GNSM di Trento e Genova per lo sviluppo di una sorgente di fasci molecolari standard da utilizzare nello studio dei processi di chemisorbimento superficiali
No full textEffetti termici nell`assorbimento multifotonico infrarosso in fasci molecolari di SF6 e CF3Br
No full textAn Opto-Thermal Study of NH3 Rotational Relaxation in NH3-He Supersonic Expansions
No full textWe have investigated the rotational relaxation of NH3 in NH3-He supersonic expansions by means of opto-thermal spectroscopy. Molecules are excited in the v3 + v4 band, around 5100 cm -1, using the third Stokes line of a Raman-shifted pulsed laser. Rotational distributions are measured for different values of the source stagnation pressure and NH3 concentration. At low rotational temperatures, populations deviate from a Boltzmann distribution. This is attributed to the reduction of para-to-ortho conversion during the expansion
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