Buffer gas

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

Attenuation of spectral interferences during laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) using an rf only collision and reaction cell

Abstract: The reduction of spectral interferences in laser ablation inductively coupled plasma mass spectrometry was investigated using an rf only hexapole as a collision and reaction cell with H2 as the reaction gas and He as a buffer gas. Argon-based polyatomic ions (ArX+) were attenuated by between 1 and 6 orders of magnitude with H2 during laser ablation experiments whilst analyte transmission under the same parameters was maintained above 80%. The amount of ArX+ attenuation for a fixed volume of reactive H2 gas was proportional to the electronegativity of parent element X. Interferences were not significantly attenuated with He. However, a change from ‘dry’ to ‘wet’ conditions in the plasma led to reactions with water molecules in the cell giving an apparent reactivity for clean He buffer gas whilst reducing the efficiency of some reactions with H2. Improved accuracy and precision were demonstrated under optimised conditions for the analysis of trace elements in sulfide and carbonate standard reference materials as a result of background interference reduction. Multi-element analysis was possible with reactive gases in the reaction cell as demonstrated by the accurate analysis, to within 15% of the recommended values for most trace elements, of candidate glass reference materials using NIST SRM glasses for calibration.

A buffer-gas cooled Bose-Einstein condensate

Abstract: We report the creation of a Bose-Einstein condensate using buffer-gas cooling, the first realization of Bose-Einstein condensation using a broadly general method which relies neither on laser cooling nor unique atom-surface properties. Metastable helium ((4)He*) is buffer-gas cooled, magnetically trapped, and evaporatively cooled to quantum degeneracy. 10(11) atoms are initially trapped, leading to Bose-Einstein condensation at a critical temperature of 5 microK and threshold atom number of 1.1 x 10(6). This method is applicable to a wide array of paramagnetic atoms and molecules, many of which are impractical to laser cool and impossible to surface cool.

Action spectroscopy and temperature diagnostics of H3+ by chemical probing

Abstract: Infrared absorption spectroscopy of few hundred H3+ ions trapped in a 22-pole ion trap is presented using chemical probing as a sensitive detection technique down to the single ion level. By exciting selected overtone transitions of the (v1=0,v2l=31)←(0,00) vibrational band using an external cavity diode laser an accurate diagnostics measurement of the effective translational and rotational temperatures of the trapped ions was performed. The absolute accuracy of the measured transition frequencies was improved by a factor of four compared to previous plasma spectroscopy measurements using velocity modulation [Ventrudo et al., J. Chem. Phys. 100, 6263 (1994)]. The observed buffer gas cooling conditions in the ion trap indicate how to cool trapped H3+ ions into the lowest ortho and para rotational states. Future experiments will utilize such an internally cold ion ensemble for state-selected dissociative recombination experiments at the heavy ion storage ring Test Storage Ring (TSR).

Computed energy and spatial statistical properties of stored ions cooled by a buffer gas

Abstract: We describe a three-dimensional model, based on the temporal invariance of the statistical properties, which allows us to calculate the spatial and energy probability densities of strongly confined ions in the presence of a buffer gas. This model is then applied to a population of ${\mathrm{Cs}}^{+}$ ions for which we compute these densities within the whole stability diagram and for various gases. In the case of helium, in particular, we show that these laws can be described by Gaussian functions, and we present the evolution of the temporal average of the spatial dispersions and ionic temperatures at the working point.

The dependence of frequency upon microwave power of wall‐coated and buffer‐gas‐filled gas cell Rb87 frequency standards

Abstract: Previous studies of a commerical passive gas cell Rb87 frequency standard showed a strong dependence of the output frequency νRb upon the microwave power Pμλ. A major conclusion of that work was that the dependence of νRb upon Pμλ was due to a line inhomogeneity effect. The line inhomogeneity interpretation suggested that substituting a wall coating for the usual buffer gas would reduce the dependence upon Pμλ. As a part of the present work, a wall coating (a form of paraffin) was used and a reduction of this dependence by a factor of 100 was obtained. The present work has led to a more convincing theoretical demonstration of the line inhomogeneity effect. The paper discusses some of the details of the analytical procedure. There are certain major requirements that a wall coating would have to satisfy if it is to be superior to the usual buffer gas, and these are discussed in the text. The advantages demonstrated by the present work indicate that further studies are warranted to determine if an improved standard could be built based on a wall coating.