scispace - formally typeset
Search or ask a question

Showing papers on "Buffer gas published in 1985"


Journal ArticleDOI
TL;DR: In this paper, a fast flow device for the study of metal cluster reactions in the gas phase is described and characterized, which utilizes metal clusters made by laser vaporization of an appropriate metal target mounted in the throat of a supersonic nozzle which exhausts into a fastflow reaction tube.
Abstract: A new fast flow device for the study of metal cluster reactions in the gas phase is described and characterized. The new device utilizes metal clusters made by laser vaporization of an appropriate metal target mounted in the throat of a supersonic nozzle which exhausts into a fast‐flow reaction tube. Reactants are injected into the flowing helium–metal cluster mixture at a point in the flow tube where shock waves have reheated the gas to roughly 320 K. Turbulence in the wake of these shock waves produces efficient mixing of the reactants. Measurement of the flow properties of this reaction tube indicate a residence time of 150–200 μs with an average density of helium buffer gas equivalent to 50–100 Torr at room temperature. Subsequent free expansion of this reaction mixture into a large vacuum chamber produces a supersonic beam with extensive cooling of the various constituents in the mixture (pyrazine was measured to be rotationally cooled to 10 K). The new cluster reaction device is, therefore, an excellent source for future studies of the jet‐cooled metal cluster reaction products themselves.

155 citations


Journal ArticleDOI
TL;DR: In this article, a small amount of hydrogen was added to the neon buffer gas in a CuBr laser to achieve a doubling of the average output power and a 1% efficiency.

55 citations


Patent
04 Dec 1985
TL;DR: In this paper, high purity nitrogen is recovered from combustion gas such as exhaust stack gases, by utilizing selective gas-permeable membranes to separate by rejection, nitrogen from the other gases present in the gas stream.
Abstract: High-purity nitrogen is recovered from combustion gas such as exhaust stack gases, by utilizing selective gas-permeable membranes to separate by rejection, nitrogen from the other gases present in the gas stream.

53 citations


Patent
23 Apr 1985
TL;DR: In this paper, a process and apparatus for removing sulfur oxide from combustion gas to form Na2SO4 and reducing the harmful effects of Na2O4 on auxiliary heat exchangers is described.
Abstract: A process and apparatus for removing sulfur oxide from combustion gas to form Na2SO4 and for reducing the harmful effects of Na2SO4 on auxiliary heat exchangers in which a sodium compound is injected into the hot combustion gas forming liquid Na2SO4 in a gas-gas reaction and the resultant gas containing Na2SO4 is cooled to below about 1150°K to form particles of Na2SO4 prior to contact with at least one heat exchanger with the cooling being provided by the recycling of combustion gas from a cooled zone downstream from the introduction of the cooling gas.

49 citations


Patent
04 Oct 1985
TL;DR: A process for producing a mixed ultrafine powder, which comprises reacting at least two metals or ceramics in the molten state with hydrogen, nitrogen, oxygen, a mixture of hydrogen and nitrogen or a mixtureof nitrogen and oxygen, is described in this paper.
Abstract: A process for producing a mixed ultrafine powder, which comprises reacting at least two metals or ceramics in the molten state with hydrogen, nitrogen, oxygen, a mixture of hydrogen and nitrogen or a mixture of nitrogen and oxygen. Each said gas or gaseous mixture being activated with a hot plasma, in an atmosphere of hydrogen gas, nitrogen gas, oxygen gas, a gaseous mixture of hydrogen and nitrogen, a gaseous mixture of nitrogen and oxygen, or a gaseous mixture of any of said gases with an inert gas under a pressure of 50 torr to 3 atmospheres to form ultrafine particles of said at least two metals or ceramics afloat in the atmospheric gas, and thereafter mixing the floating ultrafine particles of the metals or ceramics by a gas current.

34 citations


Journal ArticleDOI
TL;DR: In this paper, the beam from a rare gas halogen laser photoionizes organic molecules that have been seeded into a buffer gas, and the electron densities produced by photoionization with a microwave interferometer are analyzed with a few nanoseconds.
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...

25 citations


Journal ArticleDOI
TL;DR: In this article, 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.
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.

25 citations


Patent
27 Nov 1985
TL;DR: In this paper, high pressure xenon is used as a buffer gas in place of mercury in a high pressure sodium iodide arc discharge lamp, which has a more favorable influence than mercury on the D-line spectrum and does not react with halides in the lamp fill.
Abstract: High pressure xenon is used as a buffer gas in place of mercury in a high pressure sodium iodide arc discharge lamp. Xenon buffer gas has a more favorable influence than mercury on the sodium D-line spectrum and does not react with halides in the lamp fill. The use of xenon buffer gas increases the efficacy of the high pressure sodium iodide arc lamp.

25 citations


Journal ArticleDOI
TL;DR: In this article, the influence of the confinement parameters (a, q, Ω) on the perturbations, caused by space-charge, of the statistical properties of strongly confined Cs + ions cooled by helium buffer gas was studied.

24 citations


Journal ArticleDOI
TL;DR: Observation de resonances de Hanle pour un melange coherent de 4 ondes a l'etat fondamental de Na: leur intensite augmente et leur largeur diminue quand augmente the pression du gaz tampon.
Abstract: Hanle resonances for coherent four-wave mixing in the ground state of Na are reported whose intensity increases and whose linewidth decreases with increasing inert buffer gas pressure. In 10-mTorr Na vapor with 4 atm of argon, resonances of less than 35 mG full width at half maximum are observed. The high resolution permits direct observation of the fundamental homogeneous broadening mechanisms for the Zeeman coherences responsible for four-wave mixing.

18 citations


Journal ArticleDOI
TL;DR: In this paper, the transmission properties of a Fabry-Perot resonator, filled with Na vapor in absence of buffer gas, are systematically examined as the laser frequency is tuned across the D1 line, at different values of temperature and magnetic field.

Journal ArticleDOI
TL;DR: In this paper, an electron-beam controlled diffuse discharge system was constructed to study the behavior of pulsed discharges in the submicrosecond range in gas mixtures containing N2 as a buffer gas and small additives of electronegative gases.
Abstract: The performance of externally controlled, high‐pressure, diffuse discharges as switching elements in pulse power systems is strongly determined by the recombination and attachment processes in the fill gas. To obtain high control efficiency and fast response of the diffuse discharge switch the discharge must be attachment dominated with the attachment rate coefficient increasing with field strength. An electron‐beam controlled diffuse discharge system was constructed to study the behavior of pulsed discharges in the submicrosecond range in gas mixtures containing N2 as a buffer gas and small additives of electronegative gases. The results of experiments in N2 plus N2O were compared with values obtained with a Monte Carlo code and a rate equation calculation.

Journal ArticleDOI
TL;DR: In this article, the attachment of electrons to H2O in Ar, N2 or CH4 was investigated using a parallel-plate drift-tube apparatus and the transient voltage pulses induced by the electron motion between the electrodes were observed.
Abstract: The attachment of electrons to H2O in Ar, N2 or CH4 is investigated using a parallel‐plate drift‐tube apparatus. Electrons are produced either by irradiation of the cathode with ArF laser photons or by two‐photon‐ionization of a trace of trimethylamine in a buffer gas. The transient voltage pulses induced by the electron motion between the electrodes are observed. The electron attachment rate of H2O is determined from the ratio of transient voltage with and without H2O added to the buffer gas. The measured electron attachment rate constants of H2O in Ar increase with E/N from 2 to 15 Td. Electron attachment due to the formation of ‘‘temporary’’ negative ions in the H2O–N2 and H2O–CH4 mixture were observed. The lifetime of the negative ion was determined to be about 200 ns, whose nature is discussed. The ‘‘apparent’’ electron attachment rate constants for the formation of ‘‘temporary’’ negative ions in the H2O–CH4 gas mixture are measured for E/N from 1 to 20 Td. The electron drift velocities for the gas mixtures of H2O in various buffer gases are measured.

Journal ArticleDOI
01 Sep 1985
TL;DR: In this paper, the level crossing-technique with additional optical pumping in the ground state is demonstrated in the case of the hyperfinestructure of the 6p1P1 state of the two odd isotopes of Yb using a natural occuring isotopic mixture.
Abstract: The level crossing-technique with additional optical pumping in the ground state is demonstrated in the case of the hyperfinestructure of the 6p1P1 state of the two odd isotopes of Yb using a natural occuring isotopic mixture. The influences of the pumping process and of a buffer gas on the lc signal structure are discussed in terms of a modified Breit formula.

Journal ArticleDOI
TL;DR: In this article, the formation of a donut-shaped atom density distribution was observed when the heat sandwich oven was operated at high temperatures with an under pressure of the argon buffer gas.
Abstract: In a heat sandwich oven the metal vapor is confined to be disk shaped and is optically accessible through 360° in the plane of the disk. We have used this feature to optically measure the radial atom density distribution of sodium vapor within this type of oven, under a range of conditions. In particular, we have observed the formation of a donut‐shaped atom density distribution when the heat sandwich oven is operated at high temperatures with an under pressure of the argon buffer gas.

Journal ArticleDOI
TL;DR: In this article, the effects of buffer gas additives on the performance of an optically pumped D 2 O laser operating at 385 μm have been investigated both experimentally and by numerical simulation.
Abstract: The effects of buffer gas additives on the performance of an optically pumped D 2 O laser operating at 385 μm have been investigated both experimentally and by numerical simulation. Three gases, sulphur hexafluoride, carbon tetrafluoride, and n -hexane, were found to produce an increase of up to 40 percent in the pumping efficiency, as well as significant lengthening of the far infrared pulse. Under optimum conditions, 2.6 J in a 1 μs long pulse have been obtained. The buffer gases are shown to eliminate the vibrational deexcitation bottleneck, which in pure D 2 O leads to an accumulation of population in the upper vibrational leve and, hence, a reduction in the efficiency of absorption of the pump beam. Comparison of the observed buffer gas effects with the predictions of a numerical simulation code based on a rate equation model gives information about the constants for vibrational and rotational relaxation rates due to D 2 O-D 2 O and D 2 O-buffer gas collisions.

Patent
02 Dec 1985
TL;DR: In this article, a gas separating method and a gas separation apparatus according to the present invention effectively carry out the generation of the cryogenic effect within a plant for separating and extracting valuable gases such as nitrogen, oxygen, argon or the like from raw gas.
Abstract: A gas separating method and a gas separating apparatus according to the present invention effectively carry out the generation of the cryogenic effect within a plant for separating and extracting valuable gases such as nitrogen, oxygen, argon or the like from raw gas. For this purpose, the arrangement is such that low temperature gas within a process is subjected to a thermal exchange with the raw gas in a heat exchanger and is thermally restored; the thus restored gas is fed to a booster driven by an expansion turbine to be pressurized therein; the thus pressurized gas is cooled to the normal temperature by a cooler; the cooled gas is further cooled in the heat exchanger; and the still lower temperature gas is supplied to the expansion turbine to be adiabatically expanded, thereby generating the cryogenic effect.

Book ChapterDOI
01 Jan 1985
TL;DR: In this article, the authors described a coherent, tunable source for the VUV and XUV, which is tunable over limited regions, to wavelengths as short as 50 nm.
Abstract: Progress in the development of coherent, tunable sources for the VUV and XUV has reached a stage where these sources will soon be found in most spectroscopic laboratories. The principal methods used in generating such radiation are frequency tripling and 4-wave sum-mixing (4-WSM) in rare gases and metal vapors [1, 2]. Recently, several novel schemes have been described which overcome the lack of transmitting window materials at λ < 104 nm. For example, rare gases as well as molecular gases have been pulsed through supersonic jets [3,4], a laminar flow of H2 has been used with a curtain of Ne buffer gas [5], and a rotating pinhole has been synchronized with pulses of the primary laser [6], all providing optical transmission during XUV generation with minimum gas flow. By these various means, it has been possible to produce XUV radiation which is tunable over limited regions, to wavelengths as short as 50 nm [7].

Journal ArticleDOI
TL;DR: In this paper, two-photon ionization of cesium atoms via the resonant intermediate 7 2 P 1 2. 3 2 states has been investigated for the first time in presence of collisions with argon and helium buffer gas.

Journal ArticleDOI
TL;DR: In this paper, the lifetime of a CuBr laser with flowing neon as a buffer gas was extended to 734 h by considering the flow of the buffer gas and combined structure of the discharge tube.

Journal ArticleDOI
TL;DR: In this article, the authors proposed a method to solve the problem of "missing links" in the literature, which they termed as "missing link" problem, and achieved 1.8×10-12mol/s.
Abstract: 常圧下におけるヘリウム気流中での直流放電によって発生するヘリウムの共鳴線(λ=60nm, 21eV)を利用したガスクロマトグラフ用の光イオン化検出器を試作し,その性能を検討した.本検出器の特徴の一つは無機ガスに対して高感度を示すことである.高感度化は放電を安定化させることで達成できた.放電の安定化は,白金製の針状放電陰極と光路を持った平板状の白金製陽極とを対向させた構造にして達成した.放電は50~200μAの放電電流で安定であったが,このときの検出器のノイズレベルは1×10-13A以下であった.検出器の性能は水素,酸素及びその他の物質を測定して,これらの感度及び検出下限などから評価を行った.窒素とプロパンの検出下限はそれぞれ1.8×10-12mol/s及び1.8×10-14mol/sであった.窒素の検出感度は熱伝導度検出器の50倍以上で,プロパンの検出感度は水素炎イオン化検出器の3倍であった.

Journal ArticleDOI
TL;DR: In this article, the deposition of lead film on quartz substrates by photolysing tetraethyl lead vapor with a laser was reported, and the dependence of the deposition rate on the pressure of tetric acid, on the light intensity and on the buffer gas was measured.
Abstract: The deposition of lead film on quartz substrates by photolysing tetraethyl lead vapor with a laser is reported. The dependence of the deposition rate on the pressure of tetraethyl lead, on the light intensity and on the pressure of the buffer gas is measured. Deposition phenomena at low light intensity are discussed.

Journal ArticleDOI
TL;DR: In this article, the processes which determine the spontaneous emission in ammonia gas pumped by a CO2 laser are investigated, and it is shown that the FIR emission is dominant and the MIR emission is conditioned by this effect.
Abstract: The processes which determine the spontaneous emission in ammonia gas pumped by a CO2 laser are investigated. We demonstrate that the FIR emission is dominant and the MIR emission is conditioned by this effect. We have also observed that the CO2 emission mode and the collisions with a buffer gas have a great influence on the laser process. Some new lines have been produced and assigned.

Journal ArticleDOI
TL;DR: In this article, the role of nitrogen as a buffer gas constituent in an avalance discharge mercury bromide laser has been examined, and it was shown that a change over in excitation from electron impact dissociation of HgBr2 to energy transfer dissociation by excited nitrogen occurs at 1.5%N2.
Abstract: The role of nitrogen as a buffer gas constituent in an avalance discharge mercury bromide laser has been examined, and it is shown that a change over in excitation from electron impact dissociation of HgBr2 to energy transfer dissociation by excited nitrogen occurs at 1.5%N 2. This is explanable in terms of excitation cross-sections if considerable pumping occurs from excited states of nitrogen which are higher in energy than the metastableA state. When excitation via nitrogen is dominant, a high dischargeE/N value is needed to avoid coupling of energy to unwanted vibrational excitation.

Journal ArticleDOI
TL;DR: In this paper, the isotope selectivity and specific decomposition rates for the IR multiphoton dissociation of CDF3-CHF3 mixtures were examined as functions of various experimental parameters such as substrate pressure, composition, laser energy, irradiation geometry and buffer gas pressure.

Journal ArticleDOI
TL;DR: In this article, the authors presented a theoretical evaluation of the pumping light intensity transmitted through an inhomogeneously broadened line system submitted to a coherent microwave excitation, and developed a model for the case of rubidium 87 atoms interacting with a buffer gas and optically pumped by all components of the D1 and D2 lines.
Abstract: This paper presents a theoretical evaluation of the pumping light intensity transmitted through an inhomogeneously broadened line system submitted to a coherent microwave excitation. A model is developed for the case of rubidium 87 atoms interacting with a buffer gas and optically pumped by all components of the D1 and D2 lines. The light generated by an electrodeless lamp is considered incoherent and the coherent signal is produced in a microwave cavity. The spatial distribution of the light intensity transmitted through the absorption cell is shown to be related to the microwave magnetic-field axial-component distribution. Then the resonance curve obtained with a photodetector is a function of its shape and location. When applied to the case of a passive rubidium frequency standard, this model allows the calculation of the ultimate short-term frequency stability of the device.

Journal ArticleDOI
TL;DR: In this article, a fast electric discharge was used to obtain LAS in XeCl, XeF, and KrF excimer molecules in mixtures without a buffer gas.
Abstract: Lasing in XeCl, XeF, and KrF excimer molecules in mixtures without a buffer gas was obtained for the first time by pumping with a fast electric discharge. Lasing in XeCI molecules was observed in CCl4:Xe = 1:(400–4000) mixtures at pressures of 0.1–0.55 atm.

Patent
14 Mar 1985

Journal ArticleDOI
Zhang Jing-Yuan1, Li Qiong-ru1, Yang Jian1, Zhao Lizeng1, Ni Yu-sin1 
TL;DR: In this paper, a new experimental phenomenon -residual dip (weakening) of multiphoton ionization in Mg vapor with 3s3p 1P as an intermediate state has been observed.
Abstract: A new experimental phenomenon - resonance dip (weakening) of multiphoton ionization in Mg vapor with 3s3p 1P as an intermediate state has been observed. Photoionization and coherent radiation at 5183. 7A, accompanied by ionization dip when Mg vapor pressure was high enough, were studied simultaneously as functions of vapor pressure, laser power density and buffer gas pressure. Possible contributions to ionization dip and coherent radiation are discussed.

Journal ArticleDOI
TL;DR: Anomalous ionization has been observed following braod-band, nonresonant irradiation of an atomic barium vapor at high buffer gas pressures as mentioned in this paper, where the dependence of the densities on Ar pressure, time and Ba vapor density is suggestive of an ionization mechanism based on laser vaporization of barium droplets.