Metastable Argon Atoms Research Articles

Dissociative excitation of SiH 4 by collisions with metastable argon atoms

The excitation transfer from Ar* to SiH 4 has been studied by observing UV and visible emission in a flowing afterglow and beam apparatus. The emission rates of Sill (A 2Δ) and Si* atoms have been determined. From the nascent rovibrational distribution of SiH(A), the fractions of the available energy deposited into vibration and rotation of SiH(A) were estimated to be 2.9% and 4.4%, respectively.

Atomic Emission Characteristics of Laser-Induced Plasmas in an Argon Atmosphere at Reduced Pressure

The emission characteristics of laser-induced plasma, with the use of a Q-switched ruby laser of 1.5 J, were studied in argon atmosphere at reduced pressure. The time- and spatially resolved emission profiles were measured. In argon atmosphere at reduced pressure, the emission period of plasma is elongated to over a hundred microseconds, and the emissive region expands to more than a few tens of millimeters above the sample surface. The emission intensities of atomic lines increase severalfold in an argon atmosphere, in comparison with those obtained in air at the same pressure. Moderate confinement of plasmas and a resultant increase of emission intensities are achieved at 50 Torr. These results are explained by the chemical inertness and the thermal characteristics of the argon atmosphere and the decrease in absorption of the laser pulse by the plasma plume. The re-excitation of emissive species by collisions with metastable argon atoms seems to be less important.

Modelling of the Positive Column in an Argon‐Hexamethyl‐disiloxane dc Glow Discharge

AbstractA model is presented of the positive column of a dc glow discharge in argon with small admixtures of hexamethyldisiloxane (HMDS). The axial electric field, the ion production rates for direct‐, stepwise‐, pair‐, and Penning ionization, the densities of metastable Ar atoms and of electrons, and the wall current of HMDS ions are calculated in dependence on HMDS admixture and discharge current density. For the calculations particle balance equations were used for a diffusion determined plasma in a mixture of two gaseous components. The reaction rates for the electron collision processes were determined applying the electron distribution function calculated for pure argon. Taking into account PENNING ionization of HMDS molecules by metastable argon atoms the decrease of electric field for increasing HMDS admixtures is according to the experimen‐tally measured values. Also ion wall currents and electron densities are compared with experimen‐tal values for thin film formation rate and results of probe measurements.

Argon metastable–cadmium dihalide energy transfer collisions in a flowing afterglow

The energy dependence of dissociating collisions between argon metastable atoms and cadmium dihalide molecules have been studied in a flowing afterglow apparatus. The fluorescence spectra obtained in the range of 3000–7600 Å which result from the Ar(3P2)+CdX2 interactions indicate a dominant dissociative excitation production mechanism. The emission spectra are used to narrow the uncertainty in the currently accepted values for the dissociation energy of the CdX2 molecules. The Wigner spin rule (conservation of total electronic spin) was verified for these processes as shown by the dominance of final state triplet production as compared to the virtual absence of singlet spin state production.

Rotational energy transfer within the B 3Πg v=3 manifold of molecular nitrogen

An optical–optical double resonance experiment has been carried out to study rotationally inelastic collisions of N2 B 3Πg v=3 by argon with initial and final state resolution. Nitrogen molecules in the metastable A state are generated by collisional excitation transfer from metastable argon atoms in a flow system. Specific B state rotational levels are prepared by pulsed pump laser excitation of isolated rotational lines in the B 3Πg–A 3Σ+u (3,0) band near 688 nm. After a short delay, a probe laser interrogates the rotational populations in the B state by fluorescence excitation in the C 3Πu–B 3Πg (0,3) band near 406 nm. Collisional transfer from incident levels in all three spin–orbit manifolds of the B state was investigated. For molecules initially in the F1 (Ω=0) manifold, a preference for conservation of fine-structure label with even ΔJ changes was observed. This propensity is very pronounced for the J=0 level but is considerably relaxed for the higher levels investigated. By contrast, inelastic collisions involving the F2 (Ω=1) and F3 (Ω=2) manifolds do not exhibit a significant propensity to conserve fine-structure label. A slight residual preference for even ΔJ changes is observed in collisional transitions within the F2 manifold. These experimental results are compared to the propensity rules expected for homonuclear 3Π rotationally inelastic collisions, both in the case (a) and (b) limits. The reduction of the predicted propensities by the transition to intermediate case coupling and ‘‘orbital-correlated’’ scattering is discussed. The latter term refers to the difference potential for the N2–Ar interaction when the N2 unfilled π orbital is in or perpendicular to the triatomic plane. An unsuccessful attempt to detect collisional interelectronic transfer from the B state to the W 3Δu state by G–W laser fluorescence excitation is also reported.

Observation of orientation-dependent CF 3 chemiluminescence in the reaction of Ar( 3P 0,2) with oriented CF 3H

Orientation-dependent CF 3 chemiluminescence from 430 to 930 nm was observed for the first time in the reaction of pulsed supersonic molecular beams of metastable argon atoms and oriented CF 3H molecules. The “sideways configuration” of CF 3H as well as the “F-end configuration” was found to be more reactive than the “H-end configuration”. The Legendre expansion technique of Stolte et al. was applied up to the fourth term. A dissimilar dependence of reactivity on molecular orientation for the UV emission of CF 3 was also indicated from the present experiment.

A new type of argon ionisation detector

A new type of argon ionisation detector is described that is constructed completely of glass and Teflon, and consequently is extremely inert. The production of metastable argon atoms appears to arise from the thermionic emission of electrons from the glass surface. The volume of the detecting cell is less than 5 µl and the applied voltage lies between 1000 and 2000 V, depending on the geometry. The detector can also function with helium as the carrier gas, without the need to subject the helium to excessive purification procedures. The detector in its experimental form appears to have a potential sensitivity at least equivalent to that of the flame-ionisation detector and a linearity of at least three orders of magnitude. Preliminary experiments indicate that the argon detector will detect all substances that the original model will sense and it appears to be extremeley inexpensive to fabricate. As a result of its low dead volume, this detector should be very useful for multi-dimensional separations employing capillary columns.

Optical pumping of rare-gas metastable atom beams with a frequency-modulated multimode dye laser

Very efficient stable optical pumping of an argon metastable atom beam is achieved using a frequency-modulated multimode dye laser. Frequency modulation is accomplished by rapidly oscillating the laser output coupler using a piezoelectric translator. This technique appears attractive for use in optically pumping a wide variety of atomic species.

Liquid ionization mass spectrometry of phospholipids.

Several phosphatidylcholines (PC) and a phosphatidylethanolamine (PE) were subjected to liquid ionization (LI) mass spectrometry, in which a sample is ionized through energy transfer from metastable argon atoms under atmospheric pressure. Commercially available and synthesized, saturated or unsaturated fatty acid containing phospholipids and their mixtures were studied. A sample either as a concentrated chloroform-methanol solution or with glycerol (matrix) gave characteristic peaks such as MH+ and four fragment ions. One of the fragment ions (e.g., m/z 551 of PC 16:0, 16:0) containing both fatty acid residues has been commonly observed with other ionization methods such as CI, FD, and FAB, but the other fragment ions have not been observed in other mass spectra with one exception on desorption CI. Ions b and d (e.g., m/z 464 and 328, respectively, for PC 16:0, 16:0) contain one fatty acyl residue and the other ion containing the phosphorylcholine moiety appears at m/z 196 for PC. Thus the masses of the MH+ ion and these fragment ions provide useful structural information even in the case of a mixture. The ion b (e.g., m/z 488 of PC 18:0, 18:2) observed during an early period of heating was formed mainly by the loss of one acyl group at sn-1 of the glycerol backbone and thus may be used to differentiate the positional specificities of the constituent fatty acids. The temperature of the sample, however, should be controlled precisely, because it has a significant effect on the mass spectrum. The present method (LI) also provided useful information for a mixture of PC and PE.

液体イオン化質量分析法によるワインの直接分析および識別法の研究

Liquid ionization mass spectrometry was applied to distinguish between several types of fruits wines, such as grape wines (made from grapes), other fruits wines (made from fruits other than grapes) and grape wines with flavors. A microsyringe with a sharpened needle was used as a sample holder (Fig. 1), instead of a simple needle used previously.Three μl of a sample wine is sucked into the microsyringe and then the syringe is installed in the ion source. One μl of the sample is pushed out to form a droplet on the needle tip and is ionized by metastable argon atoms at atmospheric pressure. When the needle is heated at a heater current of 0.5 A (ca. 40°C), the minor components of wines are observed most abundantly. A mass spectrum between m/z 10 and 400 is scanned in 3 seconds and 30 mass spectra are recorded for 5 minutes. An averaged mass spectrum of 30 scans and a subtracted mass spectrum are printed out by a microcomputor system. Seven characteristic Peaks (G) at m/z 88, 105, 133, 134, 168, 178, 179 to be indicative of grape wines, 6 characteristic peaks (F) at m/z 108, 113, 118, 149, 155, 159 to be indicative of fruit wines, and 5 specific peaks (U) at m/z 214, 228, 238, 246, 253 to be indicative of non-grape property were selected from mass spectra of about 30 bottles of wines. The number of the characteristic (G and F) and specific (U) peaks were counted for each wine and summarized as three dimentional graphic representation (Fig. 6). Results indicate that the method is useful for differentiating these types of wines. The method provides more informations and is simpler and quicker than other analytical methods.

Excitation of continuum radiation in collisions of (1) electrons and (2) metastable argon atoms with H2 and D2

Measurements have been made of the spectral distribution of continuum radiation arising from collisions of low energy electrons and of metastable (3P0,2) argon atoms with hydrogen and deuterium molecules. The electron impact spectra, a(3Σ+g, v′=0) → b(3Σ+u)+hν, are in good agreement with the calculations of James and Coolidge. The spectra originating from Ar*+H2, D2 were obtained using crossed supersonic beams. In both cases, an onset at 0.065 ± 0.009 eV relative collision energy was observed. For deuterium, this onset occurs below the energy required to produce D2(a 3Σ+g) . Calculations of the spectral distributions when compared to experiment showed that, at 0.07 eV, the observed radiation arises from the first two vibrational levels of ArD* in the ratio (v′=0)/(v′=1)=4. For hydrogen at this energy, both product channels are present in the ratio ArH*/H*2=2 . At higher energy, both product channels are found in both systems with D*2 predominating in the case of D2 and ArH* in the case of H2.

Orientation of Ar(3P2) atoms by laser optical pumping

A beam of argon metastable atoms with a high degree of electron-spin polarization has been produced by optical pumping using an Oxazine 750 dye laser. The beam is suitable for the study of electron spin and orbital orientation dependences in a variety of collision processes.

Some considerations on the excitation mechanism in the inductively coupled argon plasma

The excitation conditions in the analytical observation zone of the inductively coupled argon plasma cannot be described by the model of partial local thermal equilibrium. After some general remarks on excitation models the paper analyses in tutorial fashion four alternative models proposed in the literature, featuring metastable argon atoms, radiation trapping, reaction rates and ambipolar diffusion. It is concluded that none is completely satisfactory, but that they are complementary rather than contradictory. Finally, some elements of the four models are integrated into a new model that considers the ICAP as a plasma decaying from conditions of heterogeneous disequilibrium to a situation of homogeneous thermal equilibrium.

Erratum - Electronic energy transfer between state selected metastable argon atoms and ground state krypton atoms

The excitation transfer reactions from Ar( 3 P 2 ) and Ar( 3 P 0 ) to Kr were studied in the afterglow of a pulsed discharge. The time decay of the metastable concentrations was monitored to obtain total quenching rate constants for removal of Ar( 3 P J ) by Kr. In separate experiments, Ar( 3 P 2 ) was optically depopulated in the after-glow by use of a tunable cw dye laser. Comparison of emission intensities from excited Kr levels with and without laser perturbation was used to assign relative rate constants for excitation of Kr levels by Ar( 3 P 2 ) and Ar( 3 P 0 ). The Kr excitation by Ar( 3 P 2 ) was found to be ∼40 times more efficient than by Ar( 3 P 0 ) Etude du transfert d'energie d'atomes metastables Ar( 3 P 2 et 3 P 0 ) a Kr dans la post-decharge d'un melange Ar−Kr. Mesure de la constante de decroissance de la densite d'atomes metastables pour determiner les coefficients de relaxation des atomes Ar( 3 P J ) par Kr. Experience de depeuplement du niveau Ar( 3 P 2 ) dans la phase de post-decharge a l'aide d'un laser accordable continu. Comparaison des intensites d'emission a partir des niveaux excites de Ar

Flowing afterglow studies of organic positive ions generated by penning ionization using metastable argon atoms

Penning ionization of organic molecules has been used as a convenient, clean ion source for flowing afterglow studies of organic positive ion/molecule reactions. Ionization reactions of 36 compounds were investigated, including alkanes, alkenes, ketones, ethers, chlorides and silanes. In many cases the parent ion is produced solely, but a few compounds fragment to give a daughter ion as the only ion. Some of these ions were then studied in reactions with their parent neutral molecules and in hetero-ion/molecule reactions. The combination of mild ionization and rapid thermalization in helium buffer gas circumvents complications from excited reactants. The reactions between ethylene radical ion and ethylene were examined in detail and the results are compared with both low- and high-pressure results in the literature. Rate constants and branching ratios were measured and mechanistic implications are discussed. It was determined that the loss of metastable argon by diffusion and destruction at the walls is considerably slower than the comparable loss of ions and this must be taken into account in kinetic measurements. Other reactions, including proton transfer equilibria, were also studied briefly.

Rotational and vibrational distributions of N2(C 3Πu) excited by state-selected Ar(3P2) and Ar(3P0) metastable atoms

Abstract The vibrational distributions of N 2 (C 3 Π u ) and the rotational distributions of N 2 (C 3 Π u , ???′ = 0) excited by energy transfer from state-selected argon metastable 3 P 2 or 3 P 0 atoms to nitrogen molecules were studied in the afterglow of a pulsed electrodeless discharge at 300 and 90 K. Selective depopulation of one metastable argon species was achieved by optical pumping using a tunable cw dye laser. The density of the metastable argon atoms and the intensity of the rotational lines or vibrational bands of the N 2 (C 3 Π u → B 3 Π g ) fluorescence were monitored in the afterglow. Results obtained at 90 K clearly establish a two-component rotational distribution. Rate coefficients for the excitation of the individual vibrational levels of N 2 (C 3 Π u ) by each argon metastable species were determined. The golden-rule model is unable to explain the vibrational distributions obtained by energy transfer; the vibrational population distribution of N 2 (C 3 Π u ) excited by Ar( 3 P 0 ) clearly shows this point.

ChemInform Abstract: EMISSION SPECTRA OF TRIFLUOROMETHYL RADICALS. I. UV AND VISIBLE EMISSION SPECTRA OF TRIFLUOROMETHYL OBSERVED IN THE VUV PHOTOLYSIS AND THE METASTABLE ARGON ATOM REACTION OF TRIFLUOROMETHANE

Chemischer InformationsdienstVolume 14, Issue 19 Physical Organic Chemistry ChemInform Abstract: EMISSION SPECTRA OF TRIFLUOROMETHYL RADICALS. I. UV AND VISIBLE EMISSION SPECTRA OF TRIFLUOROMETHYL OBSERVED IN THE VUV PHOTOLYSIS AND THE METASTABLE ARGON ATOM REACTION OF TRIFLUOROMETHANE M. SUTO, M. SUTOSearch for more papers by this authorN. WASHIDA, N. WASHIDASearch for more papers by this author M. SUTO, M. SUTOSearch for more papers by this authorN. WASHIDA, N. WASHIDASearch for more papers by this author First published: May 10, 1983 https://doi.org/10.1002/chin.198319045AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume14, Issue19May 10, 1983 RelatedInformation

Emission spectra of CF3 radicals. I. UV and visible emission spectra of CF3 observed in the VUV photolysis and the metastable argon atom reaction of CF3H

Two new emission bands of the CF3 radical were observed in the UV and visible regions. These emission bands were produced in the VUV photolysis of CF3H by argon resonance lines and also in the reaction of metastable argon atoms with CF3H. The UV emission bands are in the region from 180 to 300 nm. Vibrational and rotational relaxation occurred by the addition of three atmospheric pressures of helium as evidenced by the appearance of a discrete band structure. The visible emission bands are in the region 450–750 nm. The relaxation is observed by the addition of helium; however, no structure is observed in the visible emission bands (probably the band is a continuum). The sum of ΔH for the process CF3H→CF3+H and the energy of the short wavelength limit of the UV emission spectrum agree well with the energy of the incident light. It was suggested that the transition of the UV emission is from an electronically excited bound state to the ground state of CF3 and that of the visible emission is from an electronically excited bound state to an electronically excited lower repulsive state. The spectral region of the UV emission band agreed well with the absorption spectrum of CF3 observed by Glänzer et al.

Comparison of spatial distributions of argon species number densities with calcium atom and ion in an inductively coupled argon plasma

Spatial distributions of calcium atom and ion in an atmospheric pressure argon inductively coupled plasma ICP have been observed in absorption and emission measurements. The number densities of metastable argon and ground state calcium atom and ion in an ICP are estimated from the results. The spatial distributions of temperatures, electron number density, metastable argon number density, and calcium species number densities, are compared, and excitation mechanisms for argon and Ca + and Ca are discussed. Although the ionization temperature for argon is higher than other temperatures, the metastable argon number density agrees with that obtained by assuming an equilibrium at the ionization temperature corrected by taking into account the ionizations of hydrogen and oxygen. The excitation temperature is reduced almost to the gas temperature which is caused by the high collisional rate in the ICP. The thermal and non-thermal excitation mechanisms for analyte have been revealed with the spatial profiles of the emission intensities and absorbances of calcium atom and ion.

Electronic energy transfer between state selected metastable argon atoms and ground state krypton atoms

The excitation transfer reactions from Ar( 3 P 2 ) and Ar( 3 P 0 ) to Kr were studied in the afterglow of a pulsed discharge. The time decay of the metastable concentrations was monitored to obtain total quenching rate constants for removal of Ar( 3 P J ) by Kr. In separate experiments, Ar( 3 P 2 ) was optically depopulated in the after-glow by use of a tunable cw dye laser. Comparison of emission intensities from excited Kr levels with and without laser perturbation was used to assign relative rate constants for excitation of Kr levels by Ar( 3 P 2 ) and Ar( 3 P 0 ). The Kr excitation by Ar( 3 P 2 ) was found to be ∼40 times more efficient than by Ar( 3 P 0 ) Etude du transfert d'energie d'atomes metastables Ar( 3 P 2 et 3 P 0 ) a Kr dans la post-decharge d'un melange Ar−Kr. Mesure de la constante de decroissance de la densite d'atomes metastables pour determiner les coefficients de relaxation des atomes Ar( 3 P J ) par Kr. Experience de depeuplement du niveau Ar( 3 P 2 ) dans la phase de post-decharge a l'aide d'un laser accordable continu. Comparaison des intensites d'emission a partir des niveaux excites de Ar