WorldCat Identities


Works: 7 works in 8 publications in 1 language and 9 library holdings
Classifications: QC173,
Publication Timeline
Studies of non-radiative energy transfer in aromatic molecules by J. R Novak( Book )

1 edition published in 1969 in English and held by 2 WorldCat member libraries worldwide

An apparatus for automatic recording of T-T absorption spectra has been constructed and used to obtain data for several aromatic hydrocarbons in plastic media or low-temperature glasses. An apparatus for nanosecond flash photolysis and spectroscopy has been devised and built, using a Q-switched ruby laser. The first observations of absorption from the lowest excited singlet states of several aromatic hydrocarbons have been made. The spectral energy level data and lifetime and quantum yield data have been gathered together from a wide variety of sources for several dozen aromatic hydrocarbons. A comprehensive energy level diagram has been constructed for each molecule. Recent theories of radiationless transitions have been reviewed and correlations of their predictions with experimental data have been attempted in a few cases. (Author)
High intensity laser propagation in the atmosphere( Book )

2 editions published between 1966 and 1968 in English and held by 2 WorldCat member libraries worldwide

An approximate solution is found to the nonlinear, partial differential equation describing the thermal self-defocusing effect. The solution is for the special case of a flux distribution leaving the laser face, which has planar symmetry, is uniform over a semi-infinite region (simulating the interior of the beam) and falls off exponentially at the edge. The rays originating in the interior region are found to go up undeflected until they reach a height proportional to their original distance in from the edge and inversely proportional to the square root of the amount of heat per unit volume thus far deposited along the ray path. Then they begin to deflect outwards parabolically, more sharply for a larger heat density so far deposited, and also more sharply for a more steeply descending edge of the initial flux distribution. (Author)

1 edition published in 1965 in English and held by 1 WorldCat member library worldwide

The relativistic quantum theory of the symmetric top implies that the spin J of a particle state can be represented as the sum of four commuting spin operators of lengths given by the positive integers or half-integers n, n', l, l'. If (l + l') is identified with the isospin, 2(n' - n) with the strangeness, and, where applicable, ( -1) to the (n + n') power with the G parity, the simplest choices of n, n', l, l' lead to a correct description of J, I, S, G for every known strongly interacting meson or baryon state. (Author)
High intensity laser propagation in the atmosphere. iv. far wing pressure broadening( Book )

1 edition published in 1968 in English and held by 1 WorldCat member library worldwide

The residual absorption in the 10 micrometers window is considered to be due in large measure to the very far wings of the pure-rotational lines of H2O. Experimental data indicate the broadening is mainly self-broadening arising from binary collision between H2O molecules. In order to explain the relatively large absorption observed at 10 micrometers, studies were carried out based upon a model of hindered rotational motion (libration) in which the ordinary rotational motion is suppressed by the strong dipole-dipole force during close collisions. Present results give a cross section which is one-half the experimental value multiplied by a Boltzmann factor describing the probability of achieving a frequency-matching configuration. It was found that for the particular model studied that this factor is too small. However, our studies indicate a variety of possible modifications which are capable of obtaining agreement with experiment. (Author)
Triplet to triplet absorption in organic molecules for use in photochromic devices by J.L Kropp( Book )

1 edition published in 1968 in English and held by 1 WorldCat member library worldwide

The photochromic properties of several substituted aromatics and heterocyclics have been investigated. The absorption spectra, phosphorescence lifetime T-T absorption spectra and the product of triplet extinction coefficient and triplet formation efficiency, were evaluated for representative compounds. Using these data the photochromic properties of heterocyclics are compared to their hydrocarbon analogs. The values of the maximum triplet formation efficiency are lower for heterocyclics than for aromatics. However, broader T-T absorption and more efficient absorption for pumping light suggest that, on balance, heterocyclics are comparable to aromatic hydrocarbons in their effectiveness as photochromic materials. The variation of solvent induces large changes in the photochromic properties of heterocyclics thus providing a useful additional parameter for adjusting their properties. These differences also promise to shed light on the mechanism of radiationless transitions in these compounds. Recommendations for further studies to improve the photochromic properties of heterocyclics are made. (Author)
Research on triplet states and photochromism( Book )

1 edition published in 1964 in English and held by 1 WorldCat member library worldwide

The report describes research studies on the photochromic properties of the triplet states of aromatic compounds for application to the problem of flash blindness protection. Effort was concentrated on the measurement of optical densities attained as a function of flash energy, since it is this parameter which is of greatest improtance for evaluating materials for flash protection. An OD of 2 was obtained for a chrysene sample with a flash energy of 380J. Several pairs of compounds appear promising in providing broad coverage on the basis of curves constructed by adding together their T-T absorption spectra. Fatigue studies on chrysene in PMM plastic show that the samples withstand four weeks exposure to sunlight without noticeable fatigue but that the T-T absorption has decreased by about a factor of 2 or 3 after eight weeks exposure. The core effect, previously attributed to quenching by the diffusion of atmospheric oxygen into the plastic has been shown to be reversible when samples are pumped in vacuum while being either heated or irradiated with a sun lamp. A clear epoxy plastic has been developed in which the solubility of chrysene is 1/10 sq M. This may lead to thinner photochromic specimens. Fluorescence yields of more than a dozen aromatics were measured. (Author)
Triplet materials research and eye-protective system( Book )

1 edition published in 1968 in English and held by 1 WorldCat member library worldwide

The second prototype model of a 6 x 8-inch photochromic, windshield segment has been developed, tested and delivered to the Air Force. The device is designed to protect Air Force Pilots against flash blindness resulting from viewing nuclear explosions. The reversible photochromic darkening is based upon the absorption of metastable triplet states of aromatic molecules. These compounds are incorporated into a transparent plate of epoxy plastic. Two plates are attached on the outside of a 6 x 8 x 1 1/2-inch quartz block and the triplet states are excited by uv light from two flash lamps. Black-glass filters absorb the visible light from the flash lamps which would otherwise dazzle the pilot. With a 3000J excitation flash the windshield segment darkens from an open-state absorbance of 0.08 to absorbances of 0.89, 1.68, 2.18 and 2.53, respectively, at times of 50, 100, 150 and 500 microseconds after the start of the flash. The open-state transmission, optical quality and rapidity of buildup of absorbance of the present device are greatly improved compared to the performance of the windshield segment developed on the preceding contract. The windshield segment reopens to half the closed-state absorbance in 1.6 seconds. (Author)
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