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5,342
result(s) for
"Rare gases"
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Soft ionization mechanisms in flexible µ-tube plasma—elucidation of He-, Ar-, Kr-, and Xe-FµTP
The soft ionization mechanism of helium-based plasma seems to be understood while it still remains challenging in argon-based plasma, although many studies have used argon plasmas as a soft ionization source with good ionization efficiencies. In this study, helium, argon, krypton, and xenon were fed into the same discharge geometry, a flexible micro-tube plasma (FµTP), to determine the ionization mechanisms. The FµTPs operated with the named noble gases obtained comparable ionization efficiencies by MS measurements. The optical emission results showed that N2+ were the dominant ions within the helium-FµTP and noble gas ions were dominant for the other plasmas. These ions support the development of excitation and eventually stop at the end of the capillary. Therefore, Penning ionization and charge transfer between plasma and ambient air/analytes in the open atmosphere have been proven not to be the primary soft ionization mechanism. Furthermore, it was found that photoionization played a minor role in soft ionization. Using helium as a diagnosis gas in front of the discharge capillary nozzle of the FµTP, where the sample is usually positioned, shows that helium can be ignited by all of these FµTPs. This demonstrates that the excitation of a diagnosis gas as well as the ionization of analytes is independent of the type of the discharge gas. An alternative mechanism that a transient potential created by the ions is responsible for the soft ionization is subsequently proposed.
Journal Article
Simultaneous Generation at Three Wavelengths in an Optically Pumped He–Kr–Ar Medium
The results of experiments with a model of an optically pumped rare-gas laser are presented. Laser generation was produced simultaneously at three wavelengths (912.3, 893.1, and 877.7 nm) using a gas mixture consisting of 98% He (buffer gas), 1.5% Ar, and 0.5% Kr. Dependence of generation power and of the ratio of the intensities of individual lines in total generation on consumption of the gas mixture, on cuvette pressure, and on the discharge pulse repetition rate has been studied experimentally. The maximum laser power (the sum of all the wavelengths) was ~8 mW.
Journal Article
Relationship between Lennard-Jones potential and physico-chemical parameters
We developed in this paper the used methodology to describe the Lennard-Jones potential of two atoms in rare gas. In this treatment we supposed that one atom could be described by a harmonic oscillator. The interaction potential is developed at short and long ranges. The results showed that the obtained physico-chemical parameters such as the oscillator frequency, the atom mass, and the atom charge well reproduce the Lennard-Jones potential. Then the potential well depth and the effective equilibrium diameter are expressed in function of the oscillator frequency, the atom mass and charge.
Graphical abstract
Journal Article
Studying the Effects of Dissolved Noble Gases and High Hydrostatic Pressure on the Spherical DOPC Bilayer Using Molecular Dynamic Simulations
Fine-grained molecular dynamics simulations have been conducted to depict lipid objects enclosed in water and interacting with a series of noble gases dissolved in the medium. The simple point-charge (SPC) water system, featuring a boundary composed of 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC) molecules, maintained stability throughout the simulation under standard conditions. This allowed for the accurate modeling of the effects of hydrostatic pressure at an ambient pressure of 25 bar. The chosen pressure references the 240 m depth of seawater: the horizon frequently used by commercial divers, who comprise the primary patient population of the neurological complication of inert gas narcosis and the consequences of high-pressure neurological syndrome. To quantify and validate the neurological effects of noble gases and discriminate them from high hydrostatic pressure, we reduced the dissolved gas molar concentration to 1.5%, three times smaller than what we previously tested for the planar bilayer (3.5%). The nucleation and growth of xenon, argon and neon nanobubbles proved consistent with the data from the planar bilayer simulations. On the other hand, hyperbaric helium induces only a residual distorting effect on the liposome, with no significant condensed gas fraction observed within the hydrophobic core. The bubbles were distributed over a large volume—both in the bulk solvent and in the lipid phase—thereby causing substantial membrane distortion. This finding serves as evidence of the validity of the multisite distortion hypothesis for the neurological effect of inert gases at high pressure.
Journal Article
Four-Sided Symmetrical Transversely Pumped Model for Diode-Pumped Rare Gas Lasers
Diode-pumped rare gas lasers (DPRGLs) have attracted significant attention as potential high-power laser sources. This paper proposes a four-sided transverse pumping scheme to address the energy concentration degree limitations in existing side-pumped DPRGL configurations while reducing dependence on high-power narrow-linewidth pump sources. A two-dimensional model was developed and validated through comparison between simulation results and experimental data. This study systematically investigated several key factors influencing output distribution through numerical simulations. The results demonstrate that the four-sided pumping approach provides an effective pathway for developing high-power DPRGL systems.
Journal Article
Prediction of interaction energy for rare gas dimers using machine learning approaches
In our present work, we applied Machine Learning approaches to predict potential energy profiles for rare gas dimers as well as for the H
2
molecule. We designed an Artificial Neural Network (ANN) model with one and two layers, with two to eight neurons in each layer, to predict potential energy values. We compared the ANN predicted energy values with the
ab initio
data and we found an excellent agreement between the actual and predicted values. The root mean squared deviation (RMSD) values for the test data are found to be 0.10, 0.22, 0.03 and 0.47 cm
-
1
for He
2
, Ne
2
, Kr
2
and Ar
2
, respectively. Further, we observed that the ANN method is able to fit the potential energy profile for weak van der Waals dimers as well as covalently bound molecules.
Graphical abstract
Application of machine learning approaches to predict the interaction energies for rare gas dimers is tested in this study. Our results show that Artifical Neural Network modeling is able to predict the energies for these van der Waals interactions.
Journal Article
Demonstration of a diode-pumped dual-wavelength metastable krypton laser
Diode-pumped rare gas lasers are potential candidates for high-energy and high-beam quality laser systems. Currently, most investigations are focused on metastable Ar lasers. The Kr system has the unique advantages of higher quantum efficiency and lower discharge requirements for comparison. In this paper, a diode-pumped metastable Kr laser was demonstrated for the first time. Using a repetitively pulsed discharge at a Kr/He pressure of up to approximately 1500 Torr, metastable Kr atoms of more than 1013 cm–3 were generated. Under diode pumping, the laser realized a dual-wavelength output with an average output power of approximately 100 mW and an optical conversion efficiency of approximately 10% with respect to the absorbed pump power. A kinetics study involving population distribution and evolution was conducted to analyze the laser performance.
Journal Article
Measurements of Rate Constants of Energy Transfer Processes in Ar/He Plasma of Pulse-Periodic Discharge
—
The rate constants of the Ar 2
p
6
, 2
p
7
, 2
p
8
, and 2
p
9
state quenching during collisions with helium in Ar/He plasma were obtained for the first time at a gas temperature in the discharge plasma of ~410 K. Ar/He plasma is an active medium convenient for studying optically pumped lasers based on metastable atoms of heavy inert gases. Previous models did not contain the 2
p
6
and 2
p
7
levels, but they should be taken into account in double pumping schemes. Experiments show that these levels are actively populated at pressures above 100 Torr. The rate constants are determined by simulating the time dependences of the 2
p
6
, 2
p
7
, 2
p
8
, and 2
p
9
concentrations obtained experimentally by pumping the 1
s
5
→ 2
p
7
and 1
s
5
→ 2
p
s
transition using radiation of a pulsed tunable Ti:Sa laser.
Journal Article