Electronic Transition Laser Research Articles

Analytical solution of the inverse spectroscopic problem: Determination of electron moments of vibrational transitions of diatomic molecules by their probabilities

The inverse problem of spectroscopy of vibrational transitions of diatomic molecules was analytically solved on the basis of wave functions of the Morse oscillator. An example of the determination of the transition dipole-moment function by intensities of several lines of molecule vibrational-rotational spectra measured experimentally was considered. A similar approach based on simple expressions for matrix elements can be applied to consider optimal lasing conditions of the CO electronic transition laser.

Generation and laser diagnostic analysis of bismuth fluoride

Bismuth fluoride, BiF, a possible energy acceptor molecule in a chemically pumped donor–acceptor electronic transition laser has been produced at number densities exceeding 1013 molecules/cc in a flow tube reactor. A high voltage discharge was used to produce bismuth and fluorine atoms which combined in a three-body collision to form ground state BiF (X1). Laser induced fluorescence studies confirmed that BiF was formed following the discharge. A vibrational temperature of 581±35 K and rotational temperatures of 340 to 370 K were measured for BiF (X1). Laser absorption measurements were performed to obtain the number density. An absorption cross section, calculated from the physical properties of BiF, was used for the determination.

Theoretical study of the potential energy curves of the series of diatomic radicals MeIIX. I. Method and its application to BeF radical

A method for calculating potential energy curves of some low lying states of the diatomic radicals MeIIX (MeII = second group metal, X = halogen) is outlined. Because of the electronic structure of these compounds, applications to electronic transition lasers can be made. The first calculation regards the most simple example of this series, i.e. the BeF radical. The division of the procedure into separated steps allows a sure control of the quality of the results.

Theoretical Studies of Molecular Electronic Transition Lasers

The last few years have seen the discovery and rapid development of numerous electronic transition lasers, a new type of laser that offers powerful and efficient sources of coherent visible and ultraviolet radia­ tion for applications in photochemistry,. isotope separation, and con­ trolled thermonuclear fusion. In electronic transition lasers, the lasing occurs between two electronic states of a molecule, where the emission energy corresponds to a photon in the visible or ultraviolet region of the spectrum. Successful laser action requires efficient formation of the upper laser state and rapid depletion of the lower laser state. Rapid depletion of the lower laser level is necessary to maintain the population inversion in the laser, thereby maximizing the energy output. In bound-free emission a transition terminates on an unbound lower state (or at least on a repulsive portion of the potential energy curve of the lower state) and the molecule dissociates

Spectroscopic studies of the reactions Si+F2, SiH4+F2, and SiD4+F2

Spectroscopic studies of the reactions, Si+F2→SiF+F, SiH4+5/2F2→SiF+4HF, and SiD4+5/2F2→SiF+4DF are reported. Chemiluminescence, atomic absorption, and laser induced fluorescence techniques have been employed to probe these reactions. In all the reactions, SiF(A 2Σ→X 2Π) and SiF(a 4Σ→X 2Π) chemiluminescence was observed. Overall system photon yields of the SiH4/F2 reaction for producing SiF(A→X) and SiF(a→x) emission were ∼5×10−2% and 3×10−5%, respectively. The yields for the analogous SiD4/F2 reaction were about a factor of 2 lower. An energy resonance between SiF and SiH molecules was identified and studied. The results of these studies indicate that these reactions cannot be utilized to chemically produce an SiF electronic transition laser.

Pulsed blowdown—electron gun facility for low-temperature and high-pressure supersonic flow electronic transition lasers

The design of a small compact pulsed blowdown apparatus coupled to a cold cathode electron gun is described. This system allows the excitation of a gas mixture in supersonic flow at temperatures of 80 and 120 K and density of 1 amagat with a maximum electron beam current density of 20 A cm(-2) at 300 kV and pulse length of 0.5 mus. With this facility it has been possible, using aerodynamic cooling, to achieve high-power, long-pulse ultraviolet laser operation in a high-pressure active medium on XeF and Ne ii ion transitions. A strong increase in fluorescence intensity was also obtained for numerous atomic lines and molecular bands of interest for the developement of high-power, high-efficiency, visible and ultraviolet lasers.

A3Πiand B3Σ–excited states of the SO radical. Part 1.—Laser-induced fluorescence study of the A–X system; excitation spectra and lifetimes

The first observation of laser-induced fluorescence of the SO free radical is described. Using excitation with pulses of narrow-band laser radiation near 260 nm, the A3Π states of SO have been excited. Doppler-limited laser excitation spectra of SO (A3Π–X3Σ–) are reported.The radiative lifetimes τ0 of quantum resolved (v′, J′) state of the A3Π(1) and A3Π(0) states are reported; the mean value of τ0 was (16.4 ± 1.4)µs for v′= 1. Rate constants for quenching the A3Π(1) state of SO are also reported.A proposal for an SO (A–X) electronic transition laser, giving near u.v. and visible (blue) output, is discussed.

Stability criteria in metal vapor discharges

In this letter we discuss the stability criteria in recombination- and attachment-dominated metal vapor laser discharges. The mercury halide laser discharges are typical of attachment-dominated discharges, while the metal vapor exciplex lasers, like CdHg*, are typical of recombination-dominated discharges. In high-power electronic transition laser discharges, a relatively large excited-state population exists which dominates the stability of these discharges. This occurs because the excited states have a smaller ionization potential and larger ionization cross section than the ground state. As a result, multistep ionization is the dominant ionization. When three-step ionization is dominant and electron mixing of the excited states is unimportant, attachment-dominated discharges will be stable if the attachment rate β⩾mνi0, where 2<m⩾3 and νi0, is the equilibrium ionization rate. For a recombination-dominated discharge the criterion in this limit is ane0⩾mνi0 where 1.0<m⩾1.5 and a is the recombination coefficient and ne0 is the equilibrium electron density.

Chain reaction chemiluminescence of alkaline earth catalyzed N2O–CO flames

The combustion of a dry N2O–CO mixture was initiated upon mixing the gases with Mg, Ca, or Sr atoms entrained in a He carrier flow. The flames were supported in a low pressure, fast flow reactor and were marked by intense chemiluminescence corresponding to the metal atom 3P1→1S0 transition and the well known molecular bands of the metal oxides. Additionally, bands in the visible and ultraviolet were observed. By comparison with the similar banded emissions obtained upon mixing active nitrogen with metal–N2O and metal–H2O flames, it was possible to distinguish the chemiluminescence obtained in the dry N2O–CO flames from the nearly identical metal monohydroxide flame bands. The new bands are identical to those previously obtained in arcs and they are shown to correspond to transitions between excited triplet and singlet states of the diatomic metal oxides. Photon yield studies and intracavity resonant absorption measurements further indicate that these systems are prime candidates for development as a three level chemically driven electronic transition laser system.

Potential electronic transition chemical laser: parametric evaluation

Through the utilization of a generalized computer code that calculates the minimum reactive branching ratio required for a species to display optical gain, a parametric study was performed to ascertain which properties of the electronic potential curves of a heteronuclear diatomic molecule have the greatest effect on the suitability of that molecule as a potential electronic transition laser. The results of this study demonstrate that diatomic systems separate into different classes when the question of the minimum required reactive branching ratio is confronted. This separation of molecular systems was translated through the use of compiled molecular constants into a determination of which vibrational-level distribution class is most favorable for specific heteronuclear diatomic molecules to display optical gain; potential laser candidates were pointed out. In addition, a generalized gain equation for electronic transitions heteronuclear diatomic molecules that takes into account both rotational and vibrati nal partitioning was derived.

The potential for electronic transition lasers with molecules from the carbon group oxides

The potential for electronic transition lasers with molecules from the carbon group oxides

Superfluorescence in N2 and H2 electron-beam-stabilized discharges

Previous N2 and H2 electronic transition lasers have been limited to short pulse durations (10−9–10−7 sec). Using an electron-beam-stabilized discharge in argon, nitrogen (or hydrogen), and hydrogen fluoride mixtures, we have observed repetitive superfluorescent pulses lasting 5–20 μsec. Optical-cavity measurements verify that optical gain is present throughout the pulse duration at wavelengths in the nitrogen first- and second-positive band systems and in a hydrogen near-infrared band system. It is believed that HF serves to maintain a population inversion for a longer period of time by providing preferential collisional deactivation of the lower laser levels.