Helium-neon Mixtures Research Articles

Mobility of Ions in Gas Mixtures

A formula for the mobility of ions in a mixture of neutral gases is obtained as a generalization of an expression previously derived from the Boltzmann equation for ions in a pure gas (Kumar aitd Robson 1973). It is shown that Blanc's law holds only for very specialized situations. Using interaction potentials obtained in a previous work (Robson and Kumar 1973), the mobilities of K + ions in helium-neon mixtures have been calculated and the deviations from Blanc's law are discussed.

Etude de l'effet lorentz sur l'absorption de la raie de resonance λ=743Å du neon pour des pressions de quelques torr

Comparison of theoretical values of an ‘imprisonment function’ with experimental results deduced from the decay-rate constant of Ne( 3 P 0 1) atoms in helium-neon mixtures shows that the shape of the absorbed spectral line at λ = 743 A ̊ corresponds to a pure Doppler effect if the pressure is less than 0.5 torr; for larger pressures, Lorentz-broadening becomes important in the wings of the line profile.

Separation of Gas Constituents in Argon-Helium Dishcarge

Abstract When a steady state electric discharge is initiated between a pair of metal electrodes in a binary mixture of gases, the minority constituent has been found to be concentrated in the vicinity of the cathode and diluted near the anode(1–5). Considerable attention has been focussed on the helium-neon mixtures and other mixtures of rare gases. It seems that the only study in helium-argon reported so far is that of Matveeva(2) which was restricted to low gas pressures (>4 torr). In that study Matveeva found that the degree of separation of the mixture was dependent on the gas pressure only in the range 0.4–1.5 torr and independent of pressure in the range 1.5–4 torr. The degree of separation increased linearily with increasing current until a saturation is reached which was attributed to complete separation of the mixture.

Electron energy distribution functions and transport coefficients in helium and neon

The transport of electrons through gases in the regime of elastic and inelastic collisions is discussed and it is shown how the equation for the energy distribution derived by Smit follows more simply from consideration of the velocity diagram. The present analysis was applied to helium, neon and helium-neon mixtures where numerical integration techniques were employed to calculate electron energy distribution functions and transport coefficients in the range 3<or=E/p0<or=40 V cm-1 torr-1. The present results are compared with previous theoretical calculations and experimental measurements of electron transport coefficients and it is shown that approximations involved in some previous calculations can lead to significant errors.

Recombination and Ion-Conversion Processes in Helium-Neon Mixtures

Detailed studies of the time dependence of the spectral emission and that of the number density of ions have been made during the decay period of plasmas produced in helium containing various concentrations of neon atoms. The occurrence of the recombination of ${\mathrm{Ne}}^{+}$ via the collisional recombination process with a recombination coefficient proportional to the electron density is established for the first time. The studies confirm the occurrence of recombination processes previously reported for $\mathrm{He}_{2}^{}{}_{}{}^{+}$ and $\mathrm{Ne}_{2}^{}{}_{}{}^{+}$. Evidence has also been found for the population of the $4d$ levels of neon by $\mathrm{He}(2^{1}S)$ metastable atoms. New values for the rate constants of the following processes were obtained: ${\mathrm{Ne}}^{+}+2\mathrm{He}\ensuremath{\rightarrow}{(\mathrm{HeNe})}^{+}+\mathrm{He}$ (2.1 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}32}$ ${\mathrm{cm}}^{6}$ ${\mathrm{sec}}^{\ensuremath{-}1}$); ${\mathrm{Ne}}^{+}+\mathrm{Ne}+\mathrm{He}\ensuremath{\rightarrow}{(\mathrm{HeNe})}^{+}+\mathrm{Ne} \mathrm{and} \ensuremath{\rightarrow}{{\mathrm{Ne}}_{2}}^{+}+\mathrm{He}$ (3.0 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}31}$ ${\mathrm{cm}}^{6}$ ${\mathrm{sec}}^{\ensuremath{-}1}$); ${(\mathrm{HeNe})}^{+}+\mathrm{Ne}\ensuremath{\rightarrow}{{\mathrm{Ne}}_{2}}^{+}+\mathrm{He}$ (3 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}11}$ ${\mathrm{cm}}^{3}$ ${\mathrm{sec}}^{\ensuremath{-}1}$) --- all at a gas temperature of 300 \ifmmode^\circ\else\textdegree\fi{}K.

Ionization coefficients in helium, neon and helium-neon mixtures

The spatial growth of pre-breakdown ionization currents at values of E/N (E is the electric field and N the gas number density) within the range from 2·24 × 10-16 to 11·2 × 10-16 v cm2 was measured for helium, for neon and for eight different helium-neon mixtures with fractional concentrations of neon ranging from 0·05 to 0·95. For neon and all the mixtures the ionization growth was found to be accurately represented by the generalized Townsend equation. Analysis of the results in terms of this equation gave values for the primary ionization coefficient α for neon, which agreed with previously published results, and values of α/N for the mixtures, which showed that as the concentration of helium in neon increased α/N at a given E/N first increased and then passed through a maximum value. The maximum value of α/N can be typically 50% above the value for pure neon, and the concentration at which it occurs depends on the value of E/N. The secondary ionization coefficient ω/α for neon and for mixtures with large fractional concentrations (> 0·56) of neon decreased with increasing E/N, while ω/α for mixtures with small fractional concentrations of neon increased with increasing E/N. The measured ionization growth in helium showed systematic deviations from a Townsend growth, and the implications of these deviations for the determination of α from measurements of pre-breakdown currents in helium are briefly discussed.

Mechanism of Scintillation of Helium, Helium-Argon, and Helium-Neon Gas Mixtures Excited by Alpha Particles

An experimental investigation of the mechanism of scintillation of helium, helium-argon, and helium-neon mixtures excited by $\ensuremath{\alpha}$ particles has been performed. No detectable decrease in light yield was observed at pressures less than 3 atm when the applied electric field was increased in steps to $\frac{E}{p}\ensuremath{\sim}1.0$ V/cm Torr, where $E$ is the electric field and $p$ is the gas pressure. The pulse shape of helium scintillation light consists of a slow component and a spike appearing on the leading edge of the pulse. The main component of light intensity is represented by the formula $\mathrm{exp}(\ensuremath{-}\frac{t}{{\ensuremath{\tau}}_{m}})\ensuremath{-}\mathrm{exp}(\ensuremath{-}\frac{t}{{\ensuremath{\tau}}_{f}})$, where $t$ is the time in sec, ${\ensuremath{\tau}}_{m}=10\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ sec, and ${\ensuremath{\tau}}_{f}=0.3{p}^{\ensuremath{-}2.2\ifmmode\pm\else\textpm\fi{}0.3}$ sec ($p$ in Torr). Most of the emitted photons had a wavelength of less than 1050 \AA{}A. On the basis of these results, it is concluded that the emitted photons are released in the decay of excited helium molecules formed as a result of a three-body collision between a metastable and two ground-state helium atoms. A characteristic large drop in the light yield for a mixture of a small proportion of argon in a major fraction of helium can be explained by the production of argon ions by metastable helium atoms (Penning process). The same characteristic large drop for a mixture of small concentration of neon in helium seems to be caused by the excitation transfer from helium to neon atoms. The cross section ${\ensuremath{\sigma}}_{f}$ for the formation of an excited helium molecule by a three-body collision is estimated to be $50\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}23}p$ ${\mathrm{cm}}^{2}$ at 300\ifmmode^\circ\else\textdegree\fi{}K, where $p$ is in Torr. From the value of ${\ensuremath{\sigma}}_{f}$, the cross section ${\ensuremath{\sigma}}_{i}$ of the helium-argon Penning process is calculated as 41\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}16}$ and 14\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}16}$ ${\mathrm{cm}}^{2}$ by using the ratios of ${\ensuremath{\sigma}}_{i}$ to ${\ensuremath{\sigma}}_{f}$ estimated by Jesse and Sadauskis and by Northrop and Gursky, respectively.

Joule-Thomson effect in neon-helium mixtures

The increasing interest in the low-temperature uses of neon prompted the author to investigate one of its thermodynamic variables of state, the Joule-Thomson effect. He is now extending his range of experiments on that effect to mixtures of rare gases. The work reported here concerns isenthalpic values of neon-helium mixtures at high pressures

Joule-Thomson effect in neon—helium mixtures

The increasing interest in the low-temperature uses of neon prompted the author to investigate one of its thermodynamic variables of estate, the Joule—Thomson effect. He is now extending his range of experiments on that effect to mixtures of rare gases. The work reported here concerns isenthalpic values of neon-helium mixtures at high pressures.

Studies of decaying plasmas produced in neon and helium-neon mixtures

This paper reports simultaneous measurements of the time dependence of the intensities of spectral lines and that of the number density of atomic and molecular ions in decaying plasmas produced in neon and helium-neon mixtures. The measurements in neon resulting in the mobility value, μ o(Ne +) = 4.0 cm 2/V.s, at a gas temperature of 335°K, while the frequency of conversion of Ne + into Ne + 2 was found to be ν conv = 52 P 2 0 s −1. A study of the time dependences, during the neon afterglow, of the intensity of spectral lines originating from transitions from the 4 d levels strongly indicates that these levels are mainly populated by a recombination process involving Ne +. Analogous studies of the behavior of spectral lines originating from transitions from the 2 P and 3 P levels show that these energy levels are mainly populated by the dissociative recombination process Ne + 2 + e → Ne ∗ + Ne → 2Ne + hv. Preliminary studies on decaying plasmas produced in a helium-neon mixture confirmed the occurence of the processes He + 2 + Ne → Ne + + 2He and Ne + + 2He → (HeNe) + + He as previously postulated by Oskam. Moreover, these studies indicated the occurrence of the conversion process (HeNe) + + Ne + He → Ne + 2 + 2He.

On the mechanism of scintillation of helium, helium-argon and helium-neon mixtures induced by alpha impact

The scintillation of helium is explained by de-excitation of the excited molecule formed by a three body collision of a metastable atom with ground state atoms.

Cataphoresis in Helium-Neon Mixtures

Cataphoresis in He-Ne mixtures was studied spectroscopically and the measurements checked by mass spectroscopy. The pressure was varied from 6 to 90 Torr, the wall temperature from 30° to 500°C, and the current from 10 to 500 mA in quartz tubes of 9.52 and 12.7 mm diameter. The results are compared with the theoretical predictions of Druyvesteyn. Cataphoresis improves with increasing pressure, as predicted, except at pressures above 40 Torr, where the quality of cataphoresis improves only slowly with pressure. The slope of the impurity concentration curve does not change linearly with current from 20–100 mA; it increases with current at very low currents and then becomes independent of current. Because of this discrepancy between theory and experiment, a new empirical equation governing cataphoresis in the region of higher currents is suggested. An increase of temperature markedly decreases the effectiveness of cataphoresis. Increasing the tube diameter and decreasing its length also decreases the effectiveness. In order to check for a possible ``retrograde'' cataphoresis some measurements were made with He as a minor constituent in Ne. Spectroscopic observations at the cathode indicate an enhanced He concentration there (retrograde cataphoresis); mass spectroscopic analysis shows that the cataphoresis, while slight, is still normal. The extreme excitation conditions at the cathode render spectral intensity interpretations difficult if not misleading there.

Pulsed laser operation in helium-neon mixtures: H. A. H. Boot, et al., Nature, 198 (4882), 25 May 1963, 773–774

Pulsed laser operation in helium-neon mixtures: H. A. H. Boot, et al., Nature, 198 (4882), 25 May 1963, 773–774

Continuously working plant for the separation of neon-helium mixtures

This Paper studies the possibility of separating a neon-helium mixture by making use of the different solubility of the two gases in liquid nitrogen at 80 K and under increased pressure. The experiments carried out in a continuously functioning absorption column at pressures of 0.6 and 2 MPa proved the effectiveness of the process. The extraction coefficient for both gases exceeds 0.95 at fully acceptable installation sizes and liquid nitrogen consumption. The realization of the process in industrial conditions is considered as a method for obtaining neon and helium from the air.

Temperature Dependence of Ionic Mobilities in Gas Mixtures

An ion mobility tube has been used to investigate the mobilities of various ions in helium—neon mixtures at gas temperatures of 77°, 195°, and 300°K. From plots of reciprocal mobility vs fractional concentration of the gases in the mixture which exhibit the linear dependence predicted by Blanc's law, it is possible to trace the mobility of a given ion, e.g., He+, from its parent gas (helium) value, through the mixtures, to its value in the ``foreign'' gas (neon). In this way we have determined the thermal-energy mobilities of the various ions under conditions where the ion—atom interaction changes markedly (e.g., from predominantly charge transfer to polarization interaction). In addition, a search was made for the effects of (HeNe)+, previously postulated to account for deviations from Blanc's law in 300°K studies. No effects clearly attributable to (HeNe)+ ions have been observed.

Blanc's Law—Ion Mobilities in Helium-Neon Mixtures

The mobilities of ions of near thermal energies are measured in helium-neon mixtures using a drift velocity apparatus. These studies permit the investigation of ion motion in gases, e.g., ${\mathrm{He}}^{+}$ in Ne, under conditions where the charge transfer interaction is negligible compared to polarization attraction and short-range repulsion between ion and atom. In addition, the measurements provide a test of Blanc's empirical law, $\frac{1}{\ensuremath{\mu}}=\frac{{f}_{1}}{{\ensuremath{\mu}}_{1}}+\frac{{f}_{2}}{{\ensuremath{\mu}}_{2}}$, which relates the mobility $\ensuremath{\mu}$ in a binary mixture to the pure gas mobilities ${\ensuremath{\mu}}_{1}$ and ${\ensuremath{\mu}}_{2}$ and to the fractional gas concentrations ${f}_{1}$ and ${f}_{2}$. A theoretical treatment developed by Holstein is presented which shows that deviations from Blanc's law are limited to a few percent. The mobilities of ${\mathrm{He}}^{+}$, ${\mathrm{He}}_{2}^{+}$, and ${\mathrm{Ne}}_{2}^{+}$ ions are found to obey accurately Blanc's law. However, the ${\mathrm{Ne}}^{+}$ ion curve deviates markedly from the law. These deviations are explained in terms of the formation of moderately stable ${(\mathrm{He}\mathrm{Ne})}^{+}$ ions from ${\mathrm{Ne}}^{+}$. Finally, the observed mobilities of ${\mathrm{He}}_{2}^{+}$ in Ne and ${\mathrm{Ne}}_{2}^{+}$ in He are found to agree with the predictions of polarization theory.

The Propagation of Sound in Monatomic Gas Mixtures

The velocity and absorption of infinitesimal plane sound waves have been measured in neon-helium, argon-helium and krypton-helium mixtures, with molar fractions of helium from 0 to 1 in each mixture The measurements were made at 25 c, at a frequency of 700 kc/s, and at pressures from 0 1 to 2 atm The observed velocity of sound was correlated with values calculated from simple mixture thermodynamics, the measured absorption coefficients agreed with those calculated from a formula derived by Kohler

Glow discharge characteristics of helium-neon mixtures

The maintaining and breakdown potentials for a number of helium-neon mixtures have been determined over a pressure × distance (pd) range of 1 to 75 cm mm of mercury. The normal cathode fall and the minimum breakdown potential were higher for mixtures containing from 1 to 5% neon, than for either of the pure gases. At higher pd values the breakdown potential was lower for mixtures of the order of 50% helium-50% neon than for the pure gases. These results suggest reactions between the two gases affecting the ionization coefficients. Charge exchange processes, detected by Oskam in the afterglow of such mixtures, are consistent with the emission spectra of the glow discharges, and are the probable cause of the variations.

Linienbreite bei Stössen 2. Art

Abstract Measurements are described in spectral line widths in relation to energy transfer in collisions of the second kind. In particular, the conversion of electronic excitation energy into kinetic energy (and vice-versa) in helium-neon mixtures has been studied from Doppler effects upon the spectral line widths.

Neon-Helium Bands

IN the course of some experiments on the spectrum of the negative glow, some bands near 4000 A. were observed in the negative glow of neon-helium mixtures. The definite experiments were carried out in the following way.