Buffer gas

About: Buffer gas is a research topic. Over the lifetime, 3565 publications have been published within this topic receiving 47283 citations.

Ionization of organic molecules with ultraviolet lasers: A technique for generating large, well‐defined ionized volumes

Abstract: In this paper we report a technique for generating a large, homogeneous volume of ionized gas and for making time‐resolved measurements of its electron density. We also report absolute photoionization coefficients for a number of molecules. These coefficients will allow calculation of peak electron densities obtained in other ionization‐related experiments. In our technique, the beam from a rare‐gas halogen laser photoionizes organic molecules that have been seeded into a buffer gas. Ionization is accomplished by the absorption of two photons. We have analyzed the electron densities produced by photoionization with a microwave interferometer that measures the electron density in the ionized gas with a time‐resolution of a few nanoseconds. Some of the organic molecules photoionized in this work produce electron‐ion pairs with an efficiency more than five orders of magnitude higher than commonly used laboratory ionization sources such as ArF laser photoionization of NO. We have also studied the effect of at...

Method for thermally coating surfaces

Abstract: A powdery material is delivered onto the surface to be coated using a gas, without melting of the powder particles in the gas stream. The gas used contains a gas with a nitrogen content and no oxygen content, argon, neon, krypton, xenon, a gas containing hydrogen, a gas containing carbon, in particular, carbon dioxide, water vapor or mixtures of the gases just mentioned.

Time-resolved fluorescence and population measurements in laser-pumped barium vapour

Abstract: Time-resolved measurements of fluorescence and level populations have been made on barium vapour illuminated by an intense pulse of laser radiation (1 MW cm-2, 50 ns FWHM) tuned to the resonance transition of Ba I, 6s2 1S0-6s6p 1P1, at 5535 AA. Barium number densities between 1013-1015 cm-3 were investigated, using a buffer gas of helium at 100 Torr. Fluorescence was measured with two different geometrical arrangements, one allowing partial spatial resolution. In neither case did the observed fluorescence saturate with increasing laser power, although the maximum flux was more than sufficient to burn through the vapour column, as confirmed by transmission measurements. The power loss from the laser beam was found to be compatible with the scattered radiation from the pumped column in the absence of radiation trapping. In contrast to other similar experiments, no significant ionisation was detected (<5%). Time-resolved population measurements by anomalous dispersion on the 6s6p 3P2 and 6s5d 1D2 metastable levels yielded quenching cross sections for both Ba-Ba and Ba-He collisions, but gave anomalous result for the peak populations. A qualitative explanation of the fluorescence anomaly is proposed on the basis of the AC Stark effect, and it is shown that the same effect can inhibit the onset of stimulated emission to the metastable D levels.

Spectra and kinetics of the Rb2 molecule

Abstract: In an effort to evaluate the potential of the Rb2 molecule as a high power laser system, spectra of the A 1Σu to X 1Σg band have been taken in absorption and fluorescence, using 1020 atom/cm3 of noble gas as a buffer. The potential curves for both molecular states were estimated from the temperature dependence of the normalized absorption, using the classical Franck–Condon principle. The rate constant for molecular formation of the A 1Σu state is estimated to be 9×10−32 cm6/sec using xenon as a buffer gas. However, this estimate was made on the basis of the normalized fluorescence which was emitted in that band. There appears to be a significant amount of nonradiative loss from that state, as evidenced by its low fluorescence efficiency compared to the RbXe molecule. Therefore, our estimate of the molecular formation rate could be low by as much as a factor of three. These nonradiative losses might be due to predissociation from the a 3π to the repulsive χ 3Σ state. This question must be more thoroughly i...