Showing papers on "Buffer gas published in 1992"
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TL;DR: In this paper, the diameters and depths of craters in a copper sample and the amount of material ablated by the 1.06-μm radiation of a pulsed Nd: YAG laser in the buffer gases argon, neon, helium, air and nitrogen as well as the emission intensities of analyte atoms in dependence on laser power and buffer gas pressure were measured.
Abstract: We have measured the diameters and depths of craters in a copper sample and the amount of material ablated by the 1.06-μm radiation of a pulsed Nd: YAG laser in the buffer gases argon, neon, helium, air and nitrogen as well as the emission intensities of analyte atoms in dependence on laser power and buffer gas pressure. The results are correlated with corresponding data of the plasma temperatures and the relative electron densities in the plasma. Criteria for the choice of the buffer gas, the buffer gas pressure and the laser power for optical emission spectrometry of microplasmas are given.
142 citations
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29 Sep 1992TL;DR: In this paper, a gas analysis cell (110) positioned within an optical resonant cavity is described, where a flow of buffer gas is provided to protect the optical elements (120-122) in the analysis system.
Abstract: A gas analysis cell (110) positioned within an optical resonant cavity in a gas analysis system is disclosed wherein the cell (110) includes a flow of buffer gas which forms a ''dam'', thereby protecting the optical elements (120-122) in the analysis system The analysis cell (110) includes an inlet (134) for introducing a gas sample into the analysis chamber (126) of the cell Two buffer gas inlet ports (140, 142), one on each end of the cell, are provided to introduce a flow of buffer gas which is directed past optical elements (120-122) in the system adjacent the ends of the cell Two output ports (144, 146) are located at the ends of the analysis chamber (126) to remove the buffer gas and gas sample mixture The flow of buffer gas acts to confine the gas sample within the analysis chamber (126) and reduce adverse effects which occur when the gas sample comes in contact with the optical elements (120-122) of the system By providing a constant non-turbulent flow of gas adjacent the system optics, adverse changes in index of refraction are avoided, thus reducing beam steering and Schlieren effects which can occur when Brewster windows or other optics are used to constrain the gas sample within the analysis cell The buffer gas flow in the analysis cell (110) of the present invention eliminates the need for gas cell windows which have intrinsic losses This in turn minimizes losses which cause lower circulating intracavity power and signal strength
79 citations
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TL;DR: In this paper, the primary reactions of Ti + with H 2 O, NH 3, CH 3 OH, C 2 H 4, and C 3 H 6 were studied in the gas phase using a newly built SIDT-LV (selected ion drift tube with laser vaporization source) operated at thermal energies.
Abstract: The primary reactions of Ti + with H 2 O, NH 3 , CH 3 OH, C 2 H 4 , and C 3 H 6 were studied in the gas phase using a newly built SIDT-LV (selected ion drift tube with laser vaporization source) operated at thermal energies. The metal ion is produced by a standard pulsed laser vaporization source. After selection by a quadrupole mass spectrometer, Ti + is injected into a drift tube reactor with 0.7 Torr of He as buffer gas, whereupon the ion reacts with a selected reactant introduced therein
79 citations
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TL;DR: In this article, the yields of toluene-soluble material from carbon soot depend on the buffer gas as well as the pressure, and the optimum pressure was 20 Torr, under which a maximum yield of about 13 wt% was obtained.
69 citations
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TL;DR: Ion tomography studies based on spatially resolved photodissociation of benzoyl cation (C 6 H 5 CO + ) in an ion-trap mass spectrometer are presented in this article.
55 citations
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24 Nov 1992TL;DR: In this paper, an annular inert gas injection member has been provided around the reaction gas introduction holes in order to prevent deposition of a reaction byproduct on the peripheries of reaction gas injection holes.
Abstract: In order to prevent deposition of a reaction byproduct on the peripheries of reaction gas introduction holes, an annular inert gas injection member having a number of inert gas injection holes is provided around the reaction gas introduction holes. An inert gas is injected from inert gas injection holes toward an exhaust passage. This inert gas promotes a flow of an exhaust gas from a reaction space and forcibly flows toward the exhaust passage. Thus, a reaction byproduct contained in the exhaust gas is not remarkably deposited in the vicinity of the peripheries of the reaction gas introduction holes but quickly discharged into the exhaust passage. Thus, the reaction byproduct is hardly deposited around the reaction gas introduction holes.
55 citations
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TL;DR: In this article, a flow tube apparatus was used to investigate the formation of SO5− ions by gas phase ion-molecule reactions in an N2 buffer gas at 2.5 hPa pressure and room temperature (298 K).
Abstract: A flow tube apparatus was used to investigate the formation of SO5− ions by gas phase ion–molecule reactions. The reactions studied in an N2 buffer gas at 2.5 hPa pressure and room temperature (298 K) included SO2 and O2 reactions with O2−, O3−, CO3−, SO2−, and SO3− as well as their hydrates. Reaction rate constants were measured and the major product channels were identified for most reactions. The free energy changes for the hydration reactions of SO3−, SO4−, and SO5− were derived from equilibrium constant measurements. The present investigations clearly show that SO5− ions are formed in the gas phase by the association of O2 to SO3− and by the switching reaction of SO3−H2O with O2. An effective binary rate constant of 2.0×10−12 cm3 s−1 was measured for the association reaction at 2.5 hPa N2 and the rate constant of the switching reaction was 5.0×10−11 cm3 s−1. Also the reaction of O3−H2O with SO2 probably yields SO5− by a switching process having a rate constant of 1.8×10−9 cm3 s−1. The heat of formati...
54 citations
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TL;DR: In this article, the effects of storing ions at different values of the stability parameters a(z) and q(z), were studied in a quadrupole ion trap, using helium or argon as buffer.
Abstract: The effects of storing ions at different values of the stability parameters a(z) and q(z) were studied in a quadrupole ion trap, using helium or argon as buffer. A region was localized near the boundaries of the stability diagram in which the ions experience an increase in their kinetic energy. This is reflected in the occurrence both of fragmentation due to collisional activation and of a certain extent of ion loss due to unstable trajectories. The results of this excitation, referred to as 'boundary effects,' depend on the specific q(z) at which the ion storage is performed and on the buffer gas used, and point to a simpler means of obtaining tandem mass spectra with the ion trap without the need to apply resonant tickle voltages between the end-cap electrodes.
54 citations
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TL;DR: In this article, a measurement of the temperature of a typical ion cloud in a Paul trap with buffer gas cooling has been made using time-of-flight of the extracted ion cloud.
Abstract: A measurement of the temperature of a typical ion cloud in a Paul trap with buffer gas cooling has been made using time-of-flight of the extracted ion cloud. A temperature of 0·3 ± 0·1 eV was obtained for 20 00039K ions in a trap of potential well depth 60 eV with helium buffer gas at 3 × 10−2 Pa. This value is intermediate by a factor of about 10 in each direction between that of other published works using different observational methods on Paul traps operated under similar conditions. Explanations for the discrepancies are suggested. In any case, the present work indicates that sub-electronvolt temperatures can be achieved, at least for small trap loadings. The result considerably eases the design of transport systems for such ion clouds and greatly enhances the possible uses of a Paul trap collection device for highly sensitive precise experiments.
43 citations
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TL;DR: In this paper, an instrumental method for measuring the rate constants of ion-molecule reactions in an atmospheric pressure buffer gas is described, which consists of an ion mobility spectrometer, a mass spectrometers, and an assiociated gas-handling plant.
Abstract: An instrumental method for measuring the rate constants of ion-molecule reactions in an atmospheric pressure buffer gas is described here. The instrument consists of an ion mobility spectrometer, a mass spectrometer, and an assiociated gas-handling plant. The rate constants are measured by two different operational modes of the instrument. One of these does not require mass spectrometric sampling of the reaction mixture and, therefore, completely avoids measurement errors that are commonly associated with aperture sampling of a high-pressure ionized gas
41 citations
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TL;DR: In this article, a model for collisional energy transfer between ions and neutral molecules in the quadrupole radio-frequency trap was presented, which quantitatively reproduce the dependence of the ion temperature Ti on the buffer gas pressure Pn, observed on Mg+ ions and several collision partners.
Abstract: We present a novel model for collisional energy transfer between ions and neutral molecules in the quadrupole radio-frequency trap. Calculated results quantitatively reproduce the dependence of the ion temperature Ti on the buffer gas pressure Pn, observed on Mg+ ions and several collision partners (H2, He, and CH4). It is deduced from the present model that Ti is proportional to Pn-1/3 in the low-pressure range below 10-6 Torr, in good agreement with the experimental results.
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TL;DR: In this paper, a new experimental method has been developed for measurements of the rate constants of electron attachment as a function of the mean electron energy, which has been applied to the electron attachment to c-C7F14, CH3I and CH2Br2 in Xe buffer gas.
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TL;DR: In this paper, the effects of collisional cooling on the storage and detection of ions in a quadrupole ion trap mass spectrometer were examined, and four parameters that affect the storage of ions were evaluated: the pressure of the buffer gas: the qz value which established the ion trapping environment; the cooling time during which ions may collapse to the center of the trap; and the supplementary a.c. voltage used to kinetically excite selected ions.
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18 Sep 1992TL;DR: A double, back to back oriented mechanical end face seal for sealing toxic or corrosive fluids has been proposed in this article, where a relatively inert gas, such as nitrogen, is provided for use as a buffer fluid.
Abstract: A double, back to back oriented mechanical end face seal for use in sealing toxic or corrosive fluids having an intermediate buffer fluid chamber into which a relatively inert gas, such as nitrogen, is provided for use as a buffer fluid. The nitrogen gas is maintained at a pressure which exceeds the process fluid pressure by at least 10 p.s.i. and, in a preferred embodiment, spiral pumping grooves in the mating rings of each of the seals are shaped and dimensioned to pump the nitrogen buffer gas through the first seal from the intermediate chamber into the process fluid chamber and through the second seal from the intermediate chamber into the environment external to the housing and sealing area, thereby avoiding the escape of the process fluid into the intermediate buffer chamber and to the atmosphere. Contamination of the process fluid by the buffer gas may be tolerated. The buffer gas may be any relatively inert gas, a gas which is non-hazardous to the environment and also is compatible with the process fluid used; appropriate examples are nitrogen, carbon dioxide, air or one of the noble gases. The seal can be used to seal a process fluid which is either a liquid or a gas.
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TL;DR: In this article, the authors describe and discuss experiments related to the phenomenon of population trapping of ytterbium ions in the extremely long-lived 4f13 6s2 2F7/2 level ion clouds are confined in a radiofrequency trap in the presence of helium buffer gas.
Abstract: We describe and discuss experiments related to the phenomenon of population trapping of ytterbium ions in the extremely long-lived 4f13 6s2 2F7/2 level Ion clouds are confined in a radiofrequency trap in the presence of helium buffer gas The experimental set-up permits electronic ion detection, the observation of resonance fluorescence, and optical excitation at alternating wavelengths to excite either the 2S1/2–2P1/2 resonance transition, or transitions of similar wavelength which provide optical deexcitation of ions from the 2F7/2 level to the ground state The observed dependence of the population trapping rates on helium pressure is attributed to the effect of fine structure mixing collisions The transitions which deexcite ions from the 2F7/2 state show Lorentzian lineshapes with widths of 6–10 GHz and resonance wavelengths which are in significant disagreement with tabulated level positions
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TL;DR: In this paper, the operating characteristics of a self-heated copper halide laser (λ=510.6 and 578.2 nm) are described, where the copper lasant atoms are produced by electric-discharge dissociation of copper bromide that is generated in situ by flowing Ne-HBr gas mixture over copper pieces in the laser tube.
Abstract: The operating characteristics of a small self-heated copper halide laser (λ=510.6 and 578.2 nm) are described, where the copper lasant atoms are produced by electric-discharge dissociation of copper bromide that is generatedin situ by flowing Ne-HBr gas mixture over copper pieces in the laser tube. The excitation technique permits fast startup (<1 min to laser oscillation from cold), and rapid and simple control of the CuBr vapour pressure, simultaneously introducing H2 to increase the efficiency. Specific laser output energies and average powers of 12μJ cm−3 and 195 mW cm−3, respectively, are almost a factor of 2 higher than those previously reported in the literature for multi-kilohertz copper bromide lasers. A maximum power of 7.8 W was obtained from the 40 cm3 active region. At its highest efficiency (0.8%) the laser produced 6.1 W.
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TL;DR: The 4f13 6s2 2F7/2 467 nm ultra-narrow transition in laser-cooled Yb+ was determined by probing a cloud of 172Yb+ ions held in a radiofrequency trap in the presence of helium buffer gas as discussed by the authors.
Abstract: The 4f13 6s2 2F7/2–4f14 5d 2D5/2 3·43 μm infrared transition in 172Yb+ has been driven for the first time and measured to be 87 360 087(4) MHz The frequency was determined by probing a cloud of 172Yb+ ions held in a radiofrequency trap in the presence of helium buffer gas The infrared radiation was generated by difference frequency mixing in LiNbO3 The frequency measurement is part of a programme to locate the 4f14 6s 2S1/2–4f13 6s2 2F7/2 467 nm ultra-narrow transition in laser-cooled Yb+
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22 Dec 1992
TL;DR: A burner assembly has a combustion chamber in which combustion takes place in an elongate centrally disposed combustion tube as discussed by the authors, and an outer housing encases the combustion tube and provides an annular space between an inner wall of the housing and the combustion.
Abstract: A burner assembly has a combustion chamber in which combustion takes place in an elongate centrally disposed combustion tube. An outer housing encases the combustion tube and provides an annular space between an inner wall of the housing and the combustion tube. Part of the exhaust gases exiting from the combustion tube are diverted from the downstream end thereof to be returned through the annular space to the upstream end of the combustion tube. Fuel is injected into the diverted exhaust gases, volatilized when in liquid form and mixed with the diverted gases. The fuel and gas mixture is further combined with a buffer gas and becomes entrained into and mixed with a high velocity of combustion air which is injected into the upstream end of the combustion tube. The flame temperature may be monitored and the quantity of the buffer gas added may be controllably varied based on temperature readings from the monitoring process to minimize the generation of nitrous oxides.
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TL;DR: In this article, heavy target gases (neon, argon, krypton or xenon) were added in small amounts to the helium buffer gas in the quadruple ion trap, improving both the trapping efficiency of cesium iodide cluster ions of high mass-to-charge ratio and the internal energy deposition during collision-induced dussociation experiments.
Abstract: Heavy target gases (neon, argon, krypton or xenon), when added in small amounts to the helium buffer gas in the quadruple ion trap, improve both the trapping efficiency of cesium iodide cluster ions of high mass-to-charge ratio and the internal energy deposition during collision-induced dussociation experiments.
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TL;DR: A dramatic deviation from standard theory is reported from the behavior of the drift velocity as a function of frequency detuning for C{sub 2}H{sub 4}, excited into its vibrational mode by a CO{ sub 2} laser, with Kr as a buffer gas.
Abstract: In a two-component gas consisting of light-absorbing particles immersed in a buffer gas, velocity-selective excitation combined with a state-dependent kinetic collision frequency results in light-induced drift. Standard theory predicts that the drift velocity as a function of frequency detuning should have a dispersion-curve-like behavior. This was indeed found experimentally for the molecular species studied so far. We report a dramatic deviation from this behavior for C{sub 2}H{sub 4}, excited into its {nu}{sub 7} vibrational mode by a CO{sub 2} laser, with Kr as a buffer gas. The extent of the deviation is found to depend strongly upon the rotational sublevels involved. A possible explanation in terms of a three-level model is attempted but found to be unlikely.
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TL;DR: The concept of light-induced drift (LID) was introduced in this paper, which is a mechanical effect of light at the interface of the kinetic theory and laser spectroscopy.
Abstract: Publisher Summary This chapter discusses the concept of light-induced drift (LID), which is a mechanical effect of light at the interface of the kinetic theory and laser spectroscopy. The basic principle of LID, explained in terms of a two-level model for the optical absorbers, is as follows. A laser beam, the frequency of which is tuned slightly off resonance, excites those atoms that are Doppler shifted into resonance (the absorption line is assumed to be predominantly Doppler broadened); the excitation is then velocity selective. A hole is burned in the velocity distribution of the atoms in the ground state and complementarily, a peak appears in the distribution of the excited-state atoms. This results in antiparallel fluxes of excited and ground-state atoms. The mechanical action of light in the case of LID differs radically from the action of radiation pressure. In LID, the photons label only a specific velocity class and the collisions with the buffer gas transform the random atomic motion into ordered motion—that is, drift. Net transfer of photon momentum is not involved; equal but opposite momenta is imparted to the absorbing atoms and to the buffer gas.
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TL;DR: In this article, Lorentz-broadening coefficients and pressure-induced line shift coefficients of 34 individual lines have been determined for the P40 to R(40) vibration-rotation transitions in the nu(3) fundamental of CO2 using N2 as the buffer gas.
Abstract: Lorentz-broadening coefficients and pressure-induced line-shift coefficients of 34 individual lines have been determined for the P(40) to R(40) vibration-rotation transitions in the nu(3) fundamental of CO2 using N2 as the buffer gas. The parameters were derived from 0.01/cm resolution infrared absorption spectra recorded using the McMath Fourier transform spectrometer and a nonlinear, least-squares fitting algorithm. It is concluded that the N2-broadening coefficients obtained in the present study agree well with recent high resolution measurements. The results are considered to be of importance not only for predicting the infrared spectrum of the atmosphere due to CO2 absorption or emission but also for verifying theoretical calculations.
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TL;DR: In this article, the instability threshold characteristics for the ring cavity with passive weakly absorbing two-level atoms cell were derived, and several conical shells were predicted, depending on the optical arrangement, and on the buffer gas pressure.
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21 Feb 1992
TL;DR: In this paper, the authors proposed a system for supplying with inert gas a multi-stage dry-running vacuum pump, having devices for distributing the inert gas to the pump stages, in order to monitor the flow of inert gas and/or to influence the rate of flow.
Abstract: The invention concerns a device for supplying with inert gas a multi-stage dry-running vacuum pump (1) having devices for distributing the inert gas to the pump stages. In order to be able to monitor the flow of inert gas and/or to influence the rate of flow, the invention proposes a modular-construction device (36) with an inert-gas inlet, inert-gas outlets and inert-gas lines and fitted with monitoring equipment.
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TL;DR: In this paper, a new technique for measuring the cathode dark space width and the variation of ground state atomic density within it by measuring the ionization current generated by laser photoionization of neutral ground state metallic atoms is presented.
Abstract: We report on a new technique for measuring the cathode dark space width and the variation of ground state atomic density within it by measuring the ionization current generated by laser photoionization of neutral ground state metallic atoms. The technique is supported by a theoretical model of charge displacement in the dark space based on the assumption of a Lorentzian gas and thus on Langevin equations. After verifying the applicability of the theoretical approach, measurements of dark space width with respect to pressure, current and nature of the buffer gas are presented for an uranium HCD. Results of variation in density of ground state neutral uranium, in the dark space, versus current and pressure in Xe are also given. These last results are of interest when using photoionization currents in the HCD dark space for laser spectroscopy, such as photoionization studies of elements like uranium.
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30 Apr 1992TL;DR: In this article, a method for sensing oxides of nitrogen in a gas, for example, the exhaust gas of an internal combustion engine, is presented, where the measurement gas along with oxygen provided by a solid state electrochemical oxygen pumping cell is passed through an oxidation catalyst to oxidise and remove any reducing species in the gas, e.g., carbon monoxide, hydrocarbons, and hydrogen.
Abstract: The present invention relates to a structure and a method for sensing oxides of nitrogen in a gas, for example, the exhaust gas of an internal combustion engine. The measurement gas along with oxygen provided by a solid state electrochemical oxygen pumping cell (10) is passed through an oxidation catalyst (17) to oxidise and remove any reducing species in the gas, e.g., carbon monoxide, hydrocarbons, and hydrogen. The oxides of nitrogen are then sensed by a gas sensor (19) which otherwise would respond to both oxides of nitrogen and reducing species in the gas.
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18 May 1992
TL;DR: The electron monochromator is coupled to any of a number of different types of mass analyzer and used to generate slow electrons used to produce ions of target molecules for mass analysis.
Abstract: Methods and apparatuses are disclosed for mass-analysis of a sample for particular analytes of interest. An electron monochromator is coupled to any of a number of different types of mass analyzer and used to generate slow electrons used to produce ions of target molecules for mass analysis. The electrons have a narrow energy bandwidth and high intensity, even at nearly zero kinetic energy levels. The median energy level of the electrons can be preset, permitting selection of specific target molecules to be ionized. Both positive and negative-ion mass analysis can be performed. Electron-capture negative-ion mass spectrometry is particularly enhanced, with a sensitivity about three orders of magnitude greater than in results obtained using conventional negative-ion equipment. Also, a buffer gas is eliminated, allowing substantial reductions in negative-ion equipment size, weight, and energy consumption. The mass analyzer can be an ion trap, making possible sensitive analysis of low concentrations of chemical analytes, such as environmental contaminants, using a hand-held instrument. Multiple mass analyzers, or combinations of a mass analyzer with other analytical instruments such a gas chromatograph, can be coupled to the electron monochromator.
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TL;DR: Doppler-free laser spectroscopic measurement of the calcium 4 s 2 1 S 0 -4 s 4 p 1 P 1 transition at 422.673 nm by degenerate four-wave mixing is reported using an excimer-pumped dye laser as the excitation light source.
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17 Jul 1992
TL;DR: In this article, a method of reducing a nitrogen oxide content in gas is disclosed, where subject gas containing nitrogen oxide is supplied to a gas passage of a surface discharger to decompose the nitrogen dioxide content in the gas into nitrogen gas.
Abstract: A method of reducing a nitrogen oxide content in gas is disclosed. In this method, subject gas containing nitrogen oxide is supplied to a gas passage of a surface discharger to decompose the nitrogen oxide content in the gas into nitrogen gas.
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12 Nov 1992TL;DR: The high-pressure discharge lamp has a filling in a discharge vessel (1) which includes a rare gas and a metal compound (2) chosen from hafnium halide and zirconium halides.
Abstract: The high-pressure discharge lamp has a filling in a discharge vessel (1) which includes a rare gas and a metal compound (2) chosen from hafnium halides and zirconium halides. The halide evaporates and discomposes to form incandescent, condensed metal particles. The lamp may be electrodeless and may in addition contain a buffer gas as a component of its filling. Alternatively, the lamp may have internal electrodes (13) and contain mercury (12) as a buffer gas. The lamp has favorable light generating properties, in particular a good color rendering, and in addition may have a very high luminous efficacy.