Metastable Argon Atoms Research Articles

On the Rotational Distribution of N2 in the ArN2‐Discharge. The OO‐Band of the Second Positive System

AbstractThe rotational distribution of the OO‐band of the second positive system of N2 was determined by the Ornstein method in the glow discharge of an argon‐nitrogen mixture at medium pressure. Evidently, for the rotational R‐ and P‐lines some straight lines can be fitted for rotational quantum numbers between 2 and 60 according to usual representation. The slopes of the curves indicate that the Boltzmann distribution does not exist for all the levels. For each of these straight lines can be declared a value of rotational temperature. The dependence of the several rotational temperatures on the discharge current is essential lower than the corresponding dependence of the gas temperature, which is calculated by means of the energy balance. The influence of the energy transfer from metastable argon atoms to ground‐state nitrogen molecules on the rotational distribution seems to be insignificant. Comparisons with rotational distributions in pure nitrogen plasmas point at the influence of interactions between nitrogen species.

Transfer of electronic excitation in collisions of metastable argon atoms with nitrogen molecules. II

The rotational state distributions in the product molecules for collisions of metastable Ar with nitrogen are determined. The fluorescence spectra of N2*C→B emitted at the intersection of supersonic molecular beams of the reactant species is analyzed. (AIP)

Electronic energy transfer between metastable argon atoms and ground-state oxygen atoms

We have measured the rate constants for excitation of the 3p3P and 3s3S states of atomic oxygen by metastable Ar(3P2,0) to be (7.6 ± 2.6) and (8.2 ± 2.5)× 10–11 cm3 molecule–1 s–1, respectively. Using a vacuum ultraviolet absorption technique we have also determined a translational energy of ca 0.4 eV for O(3s3S). The coincidence of the two rate-constant measurements and the results of the translational-energy measurement shows that the electronic energy-transfer reaction between Ar*(3P0,2) and O(2p43P) excites primarily O(3p3P) and that >90% of the O(3s3S) excitation is by radiative cascade.

液体イオン化質量分析計によるクラスターイオンの測定

Variety of cluster ions were observed by using the liquid ionization mass spectrometer we have developed. 6,9) Metastable argon atoms were used to ionize a liquid sample at atmospheric pressure. This paper describes cluster ions composed of water, ethanol, a mixture of methanol and ethanol, acetonitrile and acetone molecules. Major ions observed were (H2O)nH+, (C2H5OH)nH+, (CH3OH)nH+(C2H5OH)m, (CH3CN)nH+H2O and (CH3COCH3)nH+H2O, respectively. Hydrogen bonds played important roles for formation of cluster ions.A molecule containing a hydroxy group combined with two molecules, because an oxygen atom of the hydroxy group combined with two hydrogen atoms. Therefore molecules of methanol and ethanol combined each other nearly freely by hydrogen bonds. In contrast, a molecule of acetonitrile or acetone was restricted to combine other molecules in production of cluster ions, because a nitrile or a carbonyl group was able to produce only one hydrogen bond. The method gives information about cluster ions which may be related with cluster molecules existed at liquid surface and/or in gas phase where hydrogen bonds are important.

Distribution of metastable argon atoms in the modified Grimm-type electrical discharge

The absorbance by metastable argon atoms of the Ar 696.543 nm line in the modified Grimm-type electrical discharge source was measured at different discharge conditions and at distances varying from 0.25 to 6 mm from the cathode. A uranium/argon hollow cathode lamp was used as primary source, which gave an argon gas temperature of 850 K when run at 12 mA. A maximum absorbance of 0.57 was found 3 mm from the cathode at 600 V, 80 mA. The magnitude of absorbance increases with discharge current while the position of maximum absorbance shifts away from the cathode with increase in discharge voltage. The quenching of metastable atoms by nitrogen is demonstrated. The spatial distribution of the intensity of four different types of spectral lines is shown. The approximate number densities of the different particles are 10 12cm −3 for metastable argon atoms, 10 16cm −3 for neutral argon atoms, 10 13 cm −3 for sputtered copper atoms and 10 14cm −3for electrons.

An investigation into the role of metastable argon atoms in the afterglow plasma of a low pressure discharge

An investigation into the behaviour of metastable argon atoms in a low pressure (250 Pa) pulsed electrical discharge was undertaken in an effort to find the cause of the persisting emission from sputtered metal atoms in the afterglow of an atomic fluorimeter. Results obtained by time-resolved emission and absorption measurements of several argon and copper spectral lines indicate that low energy electrons in the afterglow are converted to high energy electrons via the recombination of electrons with argon ions and the subsequent collisions of pairs of metastable argon atoms. The high energy electrons excite the sputtered metal atoms to give rise to a slow decaying emission tail in the afterglow. A probable change in the electron energy distribution in the afterglow may also have an effect on the observed emission. This phenomenon may be reduced by the use of a suitable quenching gas.

Collisional de-excitation of rare-gas metastable atoms Ar, Kr, Xe by molecular hydrogen and deuterium

Absolute cross sections for the collisional de-excitation of the metastable rare-gas atoms Ar (3P0.f2), Kr (3P0.2) and Xe (3P0.2) by molecular hydrogen and deuterium have been measured. The experiment employs a velocity-selected metastable atom beam and a collision chamber with a variable length. During a collision, transfer of electronic energy from the metastable atom ideas to dissociation of the target molecule. In the case of argon metastable atoms this process may be complicated by other de-excitation mechanisms.

Argon-oxygen interaction in rf sputtering glow discharges

Optical emission spectroscopy was used to study the behavior of the excited states of argon and oxygen atoms which occur in glow discharges generated during the rf diode sputtering of a zinc oxide target. The results indicate that there is an interaction between the two gases when the sputtering gas contains less than approximately 15% oxygen. A quasi-resonant transfer of excitation from a metastable argon atom to an excited, repulsive, neutral state of the oxygen molecule, which subsequently dissociates, is proposed as the interaction mechanism. Correlation with mass spectrometry data indicates that the dissociation products increase the relative rate of zinc oxide production at the target surface and therefore promote single (0001) crystallographic orientation zinc oxide film growth.

Study of Low Energy Charge Transfer Reactions of Metastable Ar Ions with Ar, Kr and Xe Atoms by Time-of-Flight Technique

Energy distributions of metastable argon atoms Ar M produced by charge transfer collisions of metastable argon ions Ar +M with Ar, Kr and Xe were measured by a time-of-flight technique at 10 eV region. The Ar M 's were found to be formed by only exothermic reactions. The analysis of the energy distributions revealed that in any case, certain excited states of atom Ar * are produced by the collisions and Ar M follows via the radiative decay from the Ar * presumably of the 3p 5 3d state. A hypothesis of one-electron-process for the charge transfer is proposed.

Molecular ion formation in decaying plasmas produced in pure argon and krypton

The formation of molecular ions Ar2+ and Kr2+ in decaying plasmas of the respective rare gases is studied at pressures between 0.2 and 3 Torr at room temperature. Measurements of the decay of He2+ in He are made to test the experimental technique used. The reaction rate coefficient for the process Ar+(2P3/2)+2 Ar→Ar2++Ar is found to be (2.35±0.2)×10−31 cm6 s−1. The corresponding reaction rate coefficient in krypton is found to be (2.2±0.2)×10−31 cm6 s−1. Using a recently proposed reaction model [Helm and Varney (1978)] for the excited fine structure state (2P1/2), the pressure dependence of the reaction rate coefficient describing the destruction Ar+(2P1/2)+2Ar→products is calculated. The pressure dependence and magnitude of the coefficient found are in agreement with the experimental findings of Liu and Conway (1975) for the above process. The process could not be studied experimentally in our system due to the low density of Ar+(2P1/2) in our discharge. The low density is inferred indirectly and the process responsible for the fast removal of the excited ion species in the argon plasma is regarded to be the superelastic collision process with slow plasma electrons Ar+(2P1/2)+e→Ar+(2P3/2)+e+0.18 eV for which a rate coefficient ≳10−7 cm3 s−1 is estimated. At late times in the afterglow a significant source of ionization is observed in argon. This source is consistent with ionizing collisions of metastable argon atoms. Its importance increased with pressure since the diffusive loss of metastable atoms becomes insignificant as the pressure is raised.

Electronic energy transfer from metastable argon atoms to ground-state nitrogen atoms

The excitation of ground-state nitrogen atoms by metastable argon atoms has been studied by vacuum ultraviolet spectroscopy in a discharge-flow reactor. Rate constants for excitation of the 2s22p2 3s2P, 2s22p2 3s4P and 2s 2p44P states were determined to be (9.0 ± 2.7) × 10−11, (1.6 ± 0.7) × 10−11 and (6.8 ± 2.9) × 10−11 cm3 molecule−1 s−1, respectively. These energy-transfer reactions involve energy defects of 0.6–1.2 eV. The results are discussed in terms of several types of curve crossings.

Study of Low Energy Charge Transfer Reactions of Metastable Argon Ions with Argon Atoms by Time-of-Flight Technique

A new technique for kinematical study of low energy charge transfer reactions is demonstrated with the reaction Ar +M +Ar→Ar M +Ar + + Δ E , where the suffix M denotes metastable states of each species. The product metastable argon atoms Ar M can be detected with a secondary electron multiplier even at very low energy, and the energy distribution of Ar M is measured by time-of-flight technique with a high resolution. The energy defect Δ E of the above reaction was determined to spread through 2 to 5 eV (exothermic). A discussion about the results obtained is given.

Chemiionization and chemilumenescence reactions of metastable argon and neon atoms with Fe(CO) 5

Crossed beam studies confirm that excited iron atoms are produced from primary collisions of metastable argon with Fe(CO) 5. Penning ionization occurs with a much larger cross section than dissociative fluorescence, and all the energeticaly accessible fragment ions are observed from ionization by metastable argon and neon.

High flux beam source of thermal rare-gas metastable atoms

A high-flux beam source has been constructed for the production of helium, neon and argon metastable atoms. The source is a DC electric discharge maintained in an expanding gas. A metastable flux of 3.5*1014, and 7.2*1013 atoms s-1 sr-1 has been achieved with most probable energies of 66, 72 and 74 meV for the helium, neon and argon sources, respectively. Time-of-flight measurements showed the widths of the respective velocity distributions to be 45%, 27% and 27%.

Kinetic reactions involving the titanium atoms in an argon-titanium hollow cathode afterglow

We have used the pulsed afterglow technique in a hollow cathode titanium-argon plasma to study the mechanisms of production and loss of the neutral and ionized titanium species. From the measurement of the decay time of the ground state titanium atom Ti(a 3F J ) density, determined by the optical absorption technique, we have deduced the value of the diffusion coefficient of titanium atoms in argon at 300 K, D 0( Ti- Ar) = 3.1 × 10 18 atoms cm -1 s -1. The analysis of the emission intensity from the excited levels of titanium ion seems to point to the fact that the principal mechanism for the production of the (Ti +) ∗ is a charge transfer process, involving Ar + ions, rather than the Penning ionization by argon metastable atoms. The excited levels of the titanium atom are populated by electron-ion recombination involving the Ti + ions.

Chemiluminescence of argon bromide. I. The emission spectrum of ArBr

In this first systematic study of the ArBr molecule, chemiluminescence spectra are generated by the reactions of metastable argon atoms with bromine-containing compounds. Three continua, due to the B (1/2)−X (1/2), B (1/2)−A (1/2) and C (3/2)−A3/2) transitions are characterized, their pressure dependences examined, and the extent of their overlap discussed in some detail. From the temperture dependence of the spectra, an upper limit for the electronic energy of the B (1/2) state is derived: TeB?61 850 cm−1.

Time-dependent theory of electronic-to-vibrational energy transfer. Application to metastable argon atoms with nitrogen molecules

Abstract The product vibrational distribution is calculated for the process Ar( 3 P) + N 2 (X) → Ar + Bi* 2 (C 3 H u ). The evolution of the molecular vibration is treated using simple time-dependent quantum mechanics. The theory fits the oscillations in the vibrational distribution observed recently by Cutshall and Muschlitz.

Transfer of electronic excitation in collisions of metastable argon atoms with nitrogen molecules

Measurements have been made of the product vibrational and rotational state distributions for the process Ar*(3P2,0)+N2(X) →Ar(1S0)+N2*(C,3Πu) by spectrometric observation of the C→B fluorescence at the intersection of supersonic beams of the reactant species over the relative kinetic energy range 0.06–0.41 eV. The results are compared with the predictions of a ’’golden rule’’ model which gives the transition probabilities in the highly impulsive limit as the product of Franck–Condon and density of states factors. Below 0.17 eV, the model fits the experimentally determined v′=0/v′=1 population ratio reasonably well. At higher energies the experimental ratio rises, however, and reaches a maximum at 0.3 eV. A statistical population of rotational levels for v′=0 corresponding to rotational temperatures of 1300 °K and 1100 °K at 0.161 and 0.089 eV relative energy, respectively, is observed, while the ’’golden rule’’ predicts considerably higher rotational excitation in each case.

Vibrational excitation of N 2(C) and N 2(B) by metastable argon atoms and the determination of the branching ratio

The reaction rates k C(υ′) for N 2(C, υ|t') (υ′ = 0, 1, 2, 3) and k B(υ″) for N 2(B, υ″) (0≤11) of the reaction: Ar( 3P 2,0) + N 2 å N 2(C, υ′) + Ar( k C(υ′)); å N 2(B, υ″) + Ar( k B(υ″)) were measured in a low pressure flowing afterglow (0.1 to 2 torr). The electronic branching ratio between N 2(B) and N 2(C) was determined to be: k B/ k C = 0.25 ± 0.15 [ k B = Σ υ″ k B(υ″), k C = Σ υ′ k C(υ′)]. It is shown that it is necessary to take into account both the quenching and the vibrational relaxation of N 2(B). The vibrational relaxation rate k υ(1) is determined to be 6.5 × 10 −12 cm 3 s −1.

On the excitation of the krypton 123.6 nm emission by metastable argon atoms

On the excitation of the krypton 123.6 nm emission by metastable argon atoms