I. I. Murav'ev

Pulsed plasma source of refractory metals

A pulsed plasma source of metal vapors is proposed, including refractory metals. The potentials of this source are illustrated on atomic rhenium, for example. A spectroscopic investigation of the spatial and temporal characteristics of the radiation arid the plasma parameters is conducted for a Re-He mixture. It is shown that the source permits one to realize a plasma over a wide range of parameters. In the spatial zone above the electrodes, the temporal evolution of the concentration distribution of Re atoms in the ground state is measured. A maximum value of 5·10+14 cm−3 is achieved.

Cadmium ion excitation in an expanding He-Cd plasma

Space-time characteristics of radiation, temperature, and electron concentration are studied for segmented excitation and subsequent recombination in an expanding He-Cd plasma. It is shown that recombination processes play the dominant role in excitation of levels. The collision of metastable helium and cadmium atoms is significant in populating the cadmium ion 42F5/2, 7/2 levels.

Level population by recombination in a pulsed plasma jet in an He-Xe mixture

Measurements have been made on the spatial and time characteristics of the radiation from an He-Xe plasma jet emerging from a discharge channel through a nozzle with a speed of about 105 cm/sec. A recombination mechanism is indicated for the line excitation by the delay between the current pulse and the production of the radiation, as well as by the substantial differences in time course for the intensities of the atomic and ionic lines and by the increase in intensity with pressure. Measurements have been made of the electron temperature and concentration, and estimates have been made of the recombination coefficients, which reflect the performance of the collisional-radiative recombination in a decaying He-Xe plasma jet.

Intensity distributions of spectral lines and elementary processes in a negative glow discharge column

The connection is established between the intensity distributions of the spectral lines along a negative glow discharge column and the individual elementary processes which take place in a low-temperature nonequilibrium plasma (direct electron excitation, step processes, recombination, collisions of the second kind, and charge exchange). The experiments were made in pure inert gases and mixtures of them at pressures 1–30 mm Hg and discharge current densities of 10−2−10+1 mA/cm2. Knowledge of the intensity distributions together with some additional data (such as the electron density, the energy distribution function of the electrons, and the population of the levels) makes it possible to estimate more accurately the rates and cross sections of the reactions which lead to excitation of the glow discharge.

Transition probabilities of neon atom in a constant electric field

The probability of 5s-3d, 5s-3p, 5p-3s, 5d-3s, 4d-3p, and 4f-3p transitions of Ne I in an electric field is calculated. It is shown that the probability of the permitted transitions 5s-3p and 5p-3s is unchanged with increase in the field from 0 to 50 kV/cm, while the probability of the forbidden transitions 5s-3d and 5d-3s is very small. In the given range of field strengths, the probability of permitted 4d-3p transitions markedly falls and intense forbidden 4f-3p transitions appear. Of the configurations considered, the electric field has most effect on those withι⩾2.

Excitation of the 7s2P1/2, 3/2 levels of Xe+ due to charge exchange in the negative glow of a glow discharge in a neon-xenon mixture

It is shown that in the negative glow of a glow discharge in mixtures of neon with xenon (xenon contents of 5.5·10−3 to 2% of the total pressure P of the mixture) with P=15 torr and discharge currents i=40 mA (cathode diameter 30 mm), the 7s2P1/2, 3/2 levels of the Xe+ ion are excited by the charge exchange reaction Xem + Ne+ → Xe+* + Ne.The effective cross section Q3/2 for excitation of the 7s2P3/2 level is estimated to lie between 10−14 and 10−15 cm2 and Q3/2≈6.5 × Q1/2, where Q1/2 is the effective cross section for excitation of the 7s2P1/2 level.

Recombination excitation of atoms in the negative glow of a neon discharge

It is shown that under anomalous discharge conditions an important contribution to excitation of radiation in a negative glow is made by dissociative recombination, which effectively populates not only the 2p and 3p, but also the higher-lying s and d, levels.

Profile of spectral-line intensity along a negative glow

The longitudinal profile of the spectral-line intensity has been measured in a plasma of a negative glow in helium, neon, and mixtures of these gases. Under the conditions of a normal glow discharge, the intensities of several spectral lines fall off exponentially toward the anode. The decay of the line intensity was used to evaluate the effective cross section for attenuation of the electron beam from the cathode dark space. There is a discussion of the mechanism for the change in the profile of the line intensity in the discharge gap at the transition on a normal glow discharge to an anomalous discharge.

Distribution of electrokinetic characteristics in a negative glow discharge plasma

ConclusionsThe fundamental features of the electron-energy spectrum in a negative glow, set forth here for helium, neon, and argon will be observed also in other neutral gases. The form of the electron-energy distribution function in a mixture of them may be substantially different [18]. The latter is also true for molecular gases [19]. However, the laws for the spatial distribution of the electrokinetic characteristics in a negative glow (presented in Sec. a-d) will hold for discharge in any gases and in any mixtures of them (if it is true that they are basically due to the effect of the electron beam from the cathode space).In this case a negative glow discharge can be successfully used for studying elementary processes occurring in a discharge plasma not only of neutral gases, but, for example, in vapors of metals and in molecular gases.

Calculation of the quadratic stark effect in krypton

The quadratic Stark effect for the seventeen levels of krypton in the 4s2p5ns-, 4s2p5np- and 4s2p5nd -configurations is calculated in the Coulomb approximation. The calculation is conducted for j-l and j-j coupling. The results obtained are found to agree satisfactorily with experiment. The Stark effect constants are given.