Simple readily manufacturable laser designs pumped by a self-sustained discharge are outlined. The outcomes of tests on laser action from exciplex molecules (ArF^*, KrCl^*, XeCl^*, and XeF^*) on electronic transitions in N₂, N₂⁺, F₂, and F and vibration transitions in CO₂ and HF are presented.

A compact (approximately equals m² of table space), surface-discharge pumped laser head has been developed and applied to pumping the XeF(C-A) transition head has been developed and applied to pumping the XeF(C-A) transition that lases in the blue-green (approximately equals 485 nm) and the 1315 nm transition of atomic iodine. Having an active length of approximately equals 50 cm, this device requires no external high voltage or current switches, and presently dissipates >8 MW per cm of surface discharge. With 5% ouput coupling (unoptimized), pulse energies >50 mJ are obtained from the CA laser and 0,7 J from the iodine laser.

A great number o recent papers were devoted to the investigation or a Penning plasma laser under the conditions or electron-beam and nuclear puinpin,g and to the experimental and theoretical investigations or plasmochemical and radiation processes in the active medium (see , tor example , [1 1 ) . But the question about maximal erriciency o the laser is opened yet and this is the main purpose or the paper.

Quasi-cw laser action with pulse duration up to 10 ms on the 1.59-, 2.45-micrometers atomic Cl transitions and 2.65-, 2.76-micrometers atomic O transitions was observed under uranium fission fragment pumping of atmospheric-pressure gas media. The mixtures of He, Ne, Ar with CCl₄, CHCl₃, CF₂Cl₂, C₂F₃Cl₃, O₂, NO, or CO were used. Nuclear pumping of high-pressure gas media at the 2.45- and 2.65-micrometers lines has been achieved for the first time. To our knowledge, the 2.76-micrometers line is a new laser line. The maximum energy parameters (output power of 130 W, power efficiency of about 0.2%) were measured for the 1.59-micrometers chlorine line in He/Ne/CCl₄ (25000/25000/1) mixture at 2 atm pressure. The minimum laser threshold was observed for this line at the thermal neutron flux of 2 X 10¹³ n/cm²s.

There took place the design and development of a three-electrode discharge laser with a gas breakdown occurring at a high-voltage pulse delivery to the intermediate electrode which is a control one and when the capacitor of the main discharge is immediately connected with two other electrodes. While investigating XeCl, KrCl excimer lasers, we got to know that this method of the active medium excitation allows to decrease the loads on the switches of the power supply system several tens of times.

Works on creating a series of lasers 'IGIA' have been completed at our institute. The series consists of the lasers of different modifications, input characteristics of them following energy in the radiation pulse 0,02-2J, pulse repetition rate 1-200 Hz, pulse duration at the half height 26-36 microsecond(s) , middle power is 0,1-200 W. The main results obtained during this long experimental cycle are presented. It is necessary to note that some of them have been published earlier.

Many applications ofthe pulsed IR-lasers are based on the irradiation selective effect on the molecular bonds ofthe chemical compounds [1-3]. In the near JR-region lasers based on the neutral inert gases atoms transitions have the most wide wavelengst set [4-5]. The practical applications of such lasers are defined by the average irradiation power level. The highest irradiation power values are achieved in the TEA-lasers with the Xe:He mixtures2-4 watts from the active volume Va =1,2 dm3 and hundreds ofrnilliwatts from V=50 cm3 [6,7]. In lasers of high pressure energy properties of the irradiation pulse and the pulses repetition rate are limited by the phenomena ofthe volume discharge degeneration to the local one, which is not applicable for the pumping purpose [6,7]. For the present time there are established mechanisms ofthe populating ofthe inert gases atoms working levels in the volume discharge plasma and main general rules of the volume discharge forming in dense gases [5-8]. The less studied questions are related with characteristic properties of the stable volume discharge forming in the pulsed-periodical regime. The present work is denoted to the study of how volume dischar ge forming conditions effects (such as pre-ionizator geometry, start ionization level, pulsed pumping generator and discharge gap properties matching ) on the volume discharge repeti tion-rate and on the average irradition power level in TEA-lasers based on Xe:He Kr:He and Ar:He mixtures.

For many technical applications high energy electron beams are required, which are generated in average an high gas pressure, that is, within 10-100 kPa. High pressure gases are the active media of known and promising lasers, characterized by high optical homogeneity, possibility of attainment of high concentration of active elements, existence of laser processes at gas elevated pressures with efficiency up to 50%. The use of relativistic electron beams resulted in the essential power increase of laser generation. However, the drawback to this method is that the electron energy is to be higher than 150-20 keY. The forming of electron high-current beams accelerated up to dozens of keY in gases is described in Refs. 1-4. Electron beams of hundreds keY energy were obtained in the Refs. 5, 6, however, the beam currents were only 1 .0-10.0 A. "Foffless" input of electron beam into an active medium is a major problem which determines the efficiency, the energy and operating characteristics of gas lasers, excited by electron beams. Forming of ' electron beams in the most active medium is one of the promising methods of solving this problem. However, for excitation of gas lasers arid metal-vapor lasers by electron beams obtained in the most active medium, it is necessary to form electron beams of hundreds keY energy and beam current of hundreds and thousands ampere. The same beams, obtained in gases, can be used for excitation of activated crystals lasers and, as well as for a number of technologies. Only few works are devoted to this problem. The electron beams of energy up to 250 keY and beam current up to 2.5kA are obtained experimentally.7 Accelerated electrons appear under the effect of shock waves at high voltage nanosecond leading edge incident on glass tubes. Investigations were carried out in the pressure range 0.1-25.2 kPa. The rapid falloff of electron current is observed at pressure more than 16 kPa. That is why, it is necessary to develop other methods of high energy electrons generation in the range of gas elevated pressures. The present paper gives the results of investigations of forming of high energy electron beams in different gases.

We present a review of the operating characteristics of the copper HyBrID laser, described in terms of the interpulse kinetics and the physical mechanisms that govern the metal seeding process.

A review of the measurements of plasma parameters (gas temperature, density, and temperature of electrons) in active media of pulsed copper vapor lasers is given. Essential disagreement exists between many published results. The possible reasons of this disagreement and experimental difficulties associated with the measurements are discussed. Some suggestions for future CVL plasma diagnostics measurements are given.

Two kinds of lasers are reported: CuBr and CuHyBrID lasers producing an average output power of 6.7 W and 9.5 W respectively of an active volume of just 4.77 cm³. These values correspond to record specific output powers of 1.4 W/cm³ and 2.0 W/cm³ respectively for these lasers and for the copper ones in general.

Design and operation of an unstable resonator lead vapor laser are discussed. Power, energy, and time behavior of the laser developed to fit multifrequency lidar sensing of the atmosphere are examined.

Pulsed laser on the transition 5d¹⁰6p²P_3/2-5d⁹6s²²D_5/2 of mercury ion HgII, which is an analog of well known laser transitions in gold and copper atoms, was studied by a double-pulse method. Experiments were carried out with discharge tubes of 4 and 8 mm bore and discharge length 30 cm with buffer gases helium and neon. It was observed that lasing in the smaller and larger tubes differs substantially. In the larger tube lasing was observed only at small time delay and never had a ring form, as it was observed earlier with smaller bore tubes. Lasing was observed at a time delay shorter than 5 microseconds but with an increase of pulse repetition rate and tube heating it disappeared. Possible mechanism of inversion formation are discussed.

Physics and techniques for producing of the pulsed runaway electron beams are considered. The main obstacle for increasing electron energies in the beams is revealed to be a self- breakdown of the e-gun's gas-filled diode. Two methods to suppress the self-breakdown and enhance the volumetric discharge producing the e-beam are offered and examined. Each of them provides 1.5 fold increase of the ceiling potential on the gun. The methods also give the ways to control several guns simultaneously. Resulting in the possibility of realizing the powerful longitudinal pumping of metal-vapor lasers on self-terminated transitions of atoms or ions.

This paper is devoted to studying the mechanism of super-fast relaxation of first Eu ion metastable states in discharge plasma in Eu-vapor-inert gas mixture. The threshold pressure of Ne for starting the first Eu ion quasi-continuous lasing at (lambda) equals1,0019 micrometers has been determined using two methods. Ratio of decay constants for de-excitation of Eu ion metastable state for He-Eu and Ne-Eu mixtures, which was close to the value (M+/-Ne)/ M+/-He))^3/2 is congruent to 11 has been determined also. The obtained results show that relaxation of Eu⁺⁷D+/-j)⁰metastable states goes either during formation of(EuX)^+* quasi molecule or during the recombination process. Structure of lower terms of the first Eu ion presented has two systems of 7 and 9 multiplet levels. Each system consists of the ground state and of resonance and metastable state groups. This system of levels corresponds to the agreed upon three-levels scheme of self-termination transition lasers.

It is shown that various types of pulsed gas discharge with large efficiency can lead to emission on B-X transitions of S₂-dimers. The investigations of the possibility of obtaining laser oscillation is presented here.

The pumping of recombination and collisional metal vapor lasers at a mixture pressure many times greater than atmospheric pressure is considered. Powerful pulse-periodic longitudinal discharge has been used to pump these lasers. It was demonstrated that under conditions of metal vapor ionizing energy many times less than that of dominand gases, the discharge stabilizes itself, thereby making it possible to pump lasers on pressures up to at least 5 atm and average linear power up to 25 kW/m. It has been proposed that the term 'keep-discharge' be adopted to refer to this discharge.

Recent advances in self-terminating metal-vapor lasers have largely resulted from the feasibility of scaling laser characteristics in the cylindrical configuration of the active medium and longitudinal pulsed discharge, which makes it possible to provide the average power W > 100W from a large bore laser tube. Increasing the active volume, however, at the expense of a larger bore for this geometry of the gas discharge channel substantially reduces the specific energy E_sp and the average specific power W_sp. Notably, the best laser characteristics have been realized with a low average specific input power P_sp. The latter ranged between 1.5 and 0.5 W/cm³ for 6-12 cm bore tubes. As P_sp was increased above a certain value, W_sp and W were found to decrease. As that took place, there appeared high radial inhomogeneities in the laser power distribution. Among the things which interfere with further increase of W, W_sp, and E_sp as the input energy is increased, are radially nonuniform overheating of the active medium and very high degree of ionization. Given high input energies, these factors will give rise to a substantial deficit of ground state metal atoms N(O) at the center of the laser tube. As P_sp is increased, the valley in the radial thermal distribution N(R) gets deeper due to ambipolar diffusion. The N(R) variation with excitation conditions has been studied experimentally for cylindrical laser tubes. The primary processes involved have been examined by means of the saturated power model. In this work we have studied laser action from Cu, I, and AuI in a tube whose configuration allows us to ameliorate the effect of a number of limiting factors on the output energy performance, on the one hand, and provides transversely separated excitation zones on the other, which, in turn, makes it possible to realize optimal thermophysical characteristics of the active medium, manipulate the spatial distribution of metal vapor, including the case of simultaneous excitation of different chemical elements.

Theoretical and experimental studies of trans-stilbene (TS) and TS-based bifluorophores are presented. The emission properties have been investigated under excimer XeCl^*-laser excitation ((lambda) equals 308 nm). It is shown that under favorable conditions, i.e. with short excitation pulses (approximately 3-4 ns), stimulated emission dominates over trans-cis photoisomerization process. The TS emission efficiency is low (approximately 4%). In this study we present the calculated absorption spectra for TS, its fluorosubstituted derivative, 2,6- difluorostilbene. Analysis of the electronic excited states shows that the internal conversion processes are the basic channel of the excitation energy degradation (k_ic equals 10¹²s^-1) for the TS molecule. The results obtained show that lasing efficiency of TS-CH₂-C120 is lower than that of C120. The mixed character of the third electron state in the bifluorophore (this is the lowest excited state of the donor fragment) results in enhanced singlet-triplet conversion between S_3* and T_11* states. This channel of the excitation energy degradation is responsible for reduced lasing efficiency of the test bifluorophore.

Different types of pump reflectors for dye lasers with xenon flashlamp pumping have been investigated experimentally. It has been shown that the flashlamp operation in the simmer mode leads to raising the main discharge temperature and increasing the lamp light output. The energy characteristics of the designed pulse-periodic dye lasers for a visible spectral range have been reported.

A method of photostability examination of dye active media is described. Quantum yield of phototransformation, relative yield of some final photoproducts, as well as laser lifetime of 2- (4pyridyl)-5 phenyl)oxazole (4PyPO) ethanol solutions were measured. These characteristics were studied as functions of dye concentration, excitation power, and pulse duration, as well as type of irradiation (by means of spontaneous or lasing). Transient T-T absorption spectra were monitored. Effects of different additions into solution of T-T absorption and photostability of the medium were investigated. Improvement in lifetime of 4PyPO active media is discussed.

A number of new fluorescence compounds suitable as efficient laser dyes for the red spectral region have been synthesized and investigated. The new dyes are distinguished by good solubility in common organic solvents and high photostability. The laser effect of the dyes has been studied by the second harmonic of YAG:Nd³⁺ laser ((lambda) equals 532 nm) as a pump source. Some of the prepared DCM derivatives and pyridine analogues are efficient laser dyes. Two compounds from a new class of phenalemines possessing good photostability and excellent laser characteristics for the 600-690 nm spectral region are reported for the first time.

In this paper we present the brief review of our investigation for the last twenty years in the field of photochemistry of laser dyes for visible spectral regions. The coumarin, rhodamine, and oxazine laser dye photoreactions which result in their photofading due to chromophore destruction and colored products formation, particularly absorbing on laser wavelength and interfering with stimulated emission, have been investigated.

Possibility of application of dyes, participating in photoprotolytic reactions, as simultaneous two-wavelength laser media at visible range was researched. Twenty-five dyes with proton accepting carbonyl group (derivatives of 7-aminocoumarin, anthrapyridone, benzanthrone, phenoxasinon) were studied. Spectral-luminescence characteristics of these dyes have been investigated at various hydrogen ion activities in ethanol. The dye structure influence on the efficiencies of various radiationless deactivation processes competing with photoprotolytic reactions, as well as on the increase of electron density on the excited oxygen atom of C equals O group were determined. Acid-base pairs, whose excitation energy losses, accompanying photoprotolytic reaction, don't exceed 30% and protolytic equilibrium shifts under excitation are maximal (pK^*-pK>4.7) were selected. Laser spectra of selected acid-base pairs under the conditions of selective and broadband cavities have been investigated. Two- wavelength laser emission (TWLE) of some acid-base pairs was achieved at spectral region of 450-640 nm. Nonlinear dependence of long-wavelength laser intensity on pumping intensity was observed. On the basis of kinetic analysis it was shown that this nonlinear dependence is caused by competition of phototprotolytic reaction with laser emission of base form, as well as by acid-base forms interaction through laser fields. The influence of cavity parameters on the competition of two laser streams was examined. Optimal conditions for TWLE of acid-base pairs in cavity with beam splitter and two selective elements were determined.

Modifications occuring in absorption and fluorescent properties of 7- diethylaminophenoxazinon-3 (I) and its fluorosubstituted analog (II) by additions of ethanol, propanol, butanol, isobutanol into nonpolar solvents (such as toluene) have been studied. Using methods developed in quantum chemistry both radiative and nonradiative relaxation constants of the electron excitation energy as well as proton accepting ability of C equals O group in molecules I and II were estimated.

Dynamics of HeI line brightness variation on time is studied at the pulsed electron beam excitation. Nonmonotonous dependence is interpreted as a result of the electron-atom collisions. Formation of stable distribution of the high-excited states population is shown, method for its characteristics calculation is proposed.

Population dynamics of neon 3s levels has been studied in Ne-H₂ active medium produced by longitudinal discharge with preionization. Effect of hydrogen and argon admixtures on population of those levels has been examined as well. Boundary conditions for inverse population on neon transition at 585 nm have been specified. Superluminescence has been obtained on a number of neon lines including those at 588.1 nm, 594.4 nm, 650.6 nm, and 653.2. nm.

The problem of electric fields effect on collisional and radiational processes is considered. It is shown that electric field can enhance and depress the effect of other anisotropic processes on polarization of atomic states. The formula for radiation intensity of Stark states by polarization tensors formalism is given as the fundamental formula of plasma polarization spectroscopy in electric field. Possibilities of polarization spectroscopy for determination of plasma anisotropic parameters are discussed.

The exciplex lasers are now the most powerful among plasma lasers from visible to VUV range. The lasers on the exciplex molecules KrF ((lambda) equals 249 nm), ArF ((lambda) equals 193 nm), XeF ((lambda) equals 351, 353 nm) are most advanced. The operating transition of this laser is B yields X. The lower (ground) operating term X is the repulsive or weak-coupled one. The highest efficiency (10%) have KrF-laser and may be ArF-laser. The XeF-laser efficiency is not so high (approximately 3%), but this laser is of interest because it has the lowest threshold of pumping among exciplex lasers. Therefore, the opportunity of nuclear pumping of XeF-laser is under discussion. The X term have in XeF molecule a rather deep well. This peculiarity leads to more strong gas temperature dependence and not high efficiency. It must be mentioned that in the models of the XeF-laser developed up to today, the temperature dependence of plasma-chemical reaction rates, and its influence on laser output is not considered in details. Besides, the only effective operating transition, not the lasing on two separate transitions ((lambda) equals 351 and 353 nm) was considered in most papers.

In this paper, we describe the principle of a technique to produce planar and volumetric plasma sources of nearly every element and results of experiments on verification of this technique. This technique is based on a generalization of the LIBORS-process (laser ionization based on resonant saturation) which because of its similarity to chemical catalytic reactions has been called CATRION (CATalytic Resonance IONization). Characteristics of vapor clouds formed near wide variety of mono-component or two-component targets in vacuum with a pulsed ruby laser were investigated. Effect of an intense KrF laser radiation on expanding tantalum-contained and, for comparison, titanium vapor clouds was studied. Photoresonance ionization in saturation mode of tantalum cloud was detected with the help of a frame camera, Langmuir probes, and spectroscopic diagnostics.

In this paper, sealed-off laser sources based on pulsed surface discharge with expanding plasma are described. Plasma dynamics is analyzed. Data on electron number density obtained in our experiments are presented. Experimental results on laser action in plasma are discussed. Formation of inverse population as well as influence of plasma expansion on level population are considered. A construction of laser tube with pulsed surface discharge and additional illumination lamp is proposed. Data obtained with such a tube are presented.

The results of investigation of electrokinetic parameters of overcooled plasma are presented in this paper. Plasma appearing in a beam type discharge as well as plasma excited by electrons beams produced by discharges of this type is considered. Mechanisms of inverse population formation and lasing on Ne atoms transitions are described also. Advantages of effective portable plasma lasers pumped by low electron beams and perspectives of their designing are discussed.

In deciding the laser type for operation in the atmosphere, one should adopt the generation frequencies which coincide with atmospheric windows of transparencies. For example, the iodine photodissociation lasers (PDL). Some parameters of these lasers are comparable with those of neodimium-doped YAG- or Co₂-lasers. Under real conditions of the laser operation when the mixing rate of sublevels of low working state exceeds significantly the relaxation rate of upper state sub levels, the spectrum of iodine laser consists of one component corresponding to the strongest transition 3 yields 4 ((nu) equals 7603.14 cm^-1). Such one-frequency spectrum is characteristic of PDL with solar, chemical or xenon lamp radiation pumping (only in the case of compensated magntic field).

Time and energy characteristics of emission in signal zone of laser navigation devices, obtained by laser beam scanning according to sinusoidal law are considered. Simple and universal expression for energy distribution in zone is derived and experimentally verified as a function of geometric parameters.

The beam angular divergence meter with CCD camera intended for beam quality test of the excimer laser has been developed. Maximum diameter of laser beam under test is 110 mm. The resolution of the instrument corresponds to diffraction limits. Wavelength region is within the limits 200-1100 nm. Preliminary meter testing has been carried out using the commercial ILGI-503 repetitively pulsed nitrogen laser and the LGN-105 CW He-Ne laser. Performance of the instrument has been demonstrated to be satisfactory both for CW operation mode and pulse operation mode.

In the study of F-H pair formation in alkali halides due to excitation of the electronic subsystem, the information of short life time states of the self-trapped excitons plays an important role. In this paper we present recent achievements in such a direction obtained by using lasers. Short pulses of laser radiation are used in the measurement of transient absorption spectra obtained by band-to-band excitation and by selective optical conversion of the short-lived defects. With nanosecond luminescence spectroscopy in double-cascade excitation, we acquired data for KJ explaining the evolution (pi) ₁ and (pi) ₂ luminescence bands at different power laser pulses. We interprete these data in terms of frequent mutual transitions between 'on-' and 'off-center' equilibrium states of self-trapped excitons. The processes of energy transfer in self-trapped excitons connected with monomers of impurity ions in mixed crystal are studied. Also, impurity recombination luminescence is investigated in fractional annealing of V_k centers at 80-200 K. It is shown that luminescence intensity of heteronuclear excitons correlates with number of own but not with heteronuclear V_k centers. Impurity luminescence in these crystals occur at exciton with core of Cl₂ type conversion to heteronuclear exciton.

For tropospheric ozone sounding with use of the differential absorption method a lidar is proposed operating at the nonconventional wavelength pairs: 271/289 nm (sum frequency of yellow and green radiation lines of copper vapor laser and second harmonic of copper vapor laser, yellow line, respectively) and 289/308 nm (308 nm is the excimer XeCl laser radiation wavelength).

Intracavity laser spectroscopy method is very effective for investigation of weak absorption spectra for detection of atoms in water and soil. Intracavity laser spectroscopy can provide both low detection limit (10⁵at/cm³) and the high speed operation of measurements that allows one to have results of measurements practically in a real time scale. In this paper the results of detection of low concentration of U-atoms are presented.

The method of broadband intracavity laser spectroscopy consists of quenching the laser emission at the absorption line, frequencies of the species placed in a broadband laser cavity. The generation bandwidth of such a laser (Delta) (nu) -(gamma) ) is much greater than the halfwidth of the spectral line under study. In this case the laser emission spectrum has sharp gaps at the frequencies of absorption lines, which can be recorded with an ordinary spectroscopic instrumentation. In the intracavity laser spectroscopy a laser itself is a nonlinear detector of weak absorption.

This paper is devoted to investigations of the interaction of laser radiation with micron-size particles suspended in distilled water. Copper vapor laser and iron, boron carbide, silver, plastic (latex) particles were used in experiments. Required light power density was created either in traditional optical set-up, where laser radiation was focused in cuvetter with suspension by the lens, or in schemes where a laser active element was used as image brightness amplifier. In the latter case, the suspension that served as one of the reflectors of resonator formed required intensity distribution due to imaging of a mask placed on another mirror of resonator. High-speed motion of absorptive particles was observed in that scheme. Theoretical estimate 10⁵-10⁶ cm/s, based on suggested mechanism of interaction, was in good agreement with experimental data. Various behavior of absorptive (iron, boron carbide, silver) and partly transparent (latex) particles under laser radiation was observed and discussed. Particularly, the treatment of quarts plate by absorptive particles and accumulation and blurring of weakly absorptive particles on quarts plate are discussed.

Results are presented on the experimental study of VUV spectra of krypton excited by a dc discharge in a capillary tube with the wall cooled to the temperature of liquid nitrogen. We studied the 120-200 nm spectral region corresponding to the transitions between the dimer lowest excited states and the weakly bound ground state, 1_u, 0_u⁺ yields 0_g⁺. Electron impact, transferring dimers from the ground state into the excited state, is shown to be an efficient excitation mechanism in the 50-650 Torr and the 10-50 mA pressure and current ranges. The spectra obtained and the calculations made corroborate the high rate of this process.

The results of an experimental study of coaxial exciplex lamps pumped by various types of discharge (the longitudinal discharge, barrier discharge, or continuous glow discharge) are presented. The mixture compositions and pressures as well as the pumping pulse parameters have been optimized for the production of radiation with (lambda) equals 350, 308, 249, 222, and 193 nm. Exciplex lamps with a radiating surface area of 570, 840 and 1300 cm² have been created. The average radiation power achieved for (lambda) equals 222 nm is up to 4 W and for (lambda) approximately 308 and 350 nm is approximately 10 W. The possibility of an inductive energy store with a semiconductor opening switch being used for pumping a longitudinal-discharge-based exciplex lamp has been demonstrated.

A novel approach to the development of continuously tunable laser source is presented. Laser output tunable over the spectal range from 300 to 500 nm is proposed to be obtained by SRS conversion of XeCl-laser wavelength in high pressure gas mixture with spectral overlapping of different Stokes lines. The efficiency of such a laser source can reach 1% within entire range of tuning whereas output energy can exceed 1J. The first experiments performed in this area are described.

Barium vapor emission in the vicinity of the (5d6p¹P₁^COP-6s¹S₀) and (6p¹P₁^COP-6s¹S₀) resonance transitions excited by a XeCl^* laser has been studied experimentaly. IR radiation ((lambda) equals 2315.8 nm) assigned to the Ba (7p¹P₁^COP-7s¹S₀) transition has been detected. Four-wave parametric oscillation is assumed to be responsible for the Ba emission. Observations of the interaction range between UV pump radiation and Ba vapor have shown the green emission to be produced from a great number of narrow regions. This effect is attributable either to self- focusing or inversion threads.