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Lasing was observed in vapors of new organic compounds: para-terphenyl, 2-phenylbenzoxazole, 2-(n-tolyl) benzoxazole, 2-(n-methoxyphenyl) benzoxazole, 2-(n-dimethylaminophenyl) benzoxazole, 2-biphenylbenzoxazole, 2-(α-naphthyl) benzoxazole, and also 1,4-di(n-phenylethynyl) benzole, and paraquaterphenyl pumped transversely by XeCl* excimer laser radiation at λp = 308 nm. The lasing bands without tuning covered the 330–370 nm range. The shortest-wavelength maximum (333.5 nm) was observed for 2-(n-methoxyphenyl) benzoxazole. An analysis was made of the lasing ability of the molecules.

A study is made of the possibility of improving the laser properties of dyes pumped by the radiation of a copper-vapor laser, the choice of dye mixtures optimal from the point of view of producing stimulated emission, and the influence of the solvent on these properties, the aim being to obtain optimal energy parameters in an instrument based on a copper-vapor laser and an optical attachment.

The nature of theπ→π* transitions in the spectra of quinoxaline 1-N-oxides as compared with unoxidized quinoxalines was examined on the basis of an experimental, study and calculation by the Pariser-Parr-Pople configurational interaction method.

diagrammes Sc203--Ln20~," J. Solid State Chem., 26, 311-319 (1978). I0. M. J. Weber and T. E. Varitimos, "Optical spectra and intensities of Nd 3+ in YAI03," J. Appl. Phys., 42, 4996-5005 (1971) 0 Ii. P. A. Arsen'ev---and K. E. Binert, "Synthesis and optical properties of gadolinium alumihate single crystals doped with neodymium," Zh. Prikl. Spektrosk., 17, 1084-1087 (1972). 12. A. A. Kaminskii, A. O. Ivanov, S. E. Sarkisov, et al., "Combined studies on the spectral generation characteristics of LnAIO3 crystals containing Nd3+, '' Zh. Eksp. Teor. Fiz., 71, 984-1002 (1976).

The electronic structure, band characteristics, and interaction mechanism in aniline-nitrobenzene and nitrobenzene-phenol complexes are discussed. The discussion is based on the results from calculations by the Huckel and self-consistent field methods [7, 8].

The CNDO/2 method (complete neglect of differential overlap for valence electrons) [1] was used to calculate the models of molecules of toluene (I), nitrobenzene (II), o-nitrotoluene (III), and 2,4-dinitrotoluene (IV). The π- and σ-electronic structure of these molecules was discussed in the ground electronic state. A comparison of the total energies of various forms of III and IV molecules was used to determine the most likely pathway of conversion of the aci-nitro form into the nitro form and to estimate the activation energy of this process.

Quantum chemistry methods are used to calculate the cross section for stimulated emission σ(ν) and the Einstein coefficients B(ν) for several substituted forms of oxazole, oxadiazole, naphthalene, pyrene, and other molecules. It is shown that introduction of electron-donor and phenylethynyl substituents into molecules of heteroaromatic and aromatic compounds, respectively, increases considerably both σ(ν) and B(ν) and imparts lasing ability to nonlasing compounds. A criterion is established for the oscillator strength of an electronic transition which must be satisfied if a compound is to have the lasing ability.

Lasing was observed in pentane-stabilized vapors of 1,4-di[2-(5-phenyloxazolyl)]benzene (POPOP) and 1,4-di(benzoxazol-2'-yl)benzene (BOPBO) pumped by KrF* excimer laser radiation (λp = 248 nm). An investigation was made of the dependences of the threshold pump power density Wp.th on the pentane pressure, on temperature, and on the vapor pressure of the lasing substance at pump wavelengths λp = 248, 308, 337, and 350 nm. In the case of BOPBO the minimum threshold power density was Wp.th = 250 kW/cm2.