Abstract: Aimed at teaching the novice researcher enough laser spectroscopy to enable him to contribute to current laboratory projects. Chapters contain problem sets, new materials on signal-to-noise ratio, resonant ionization spectroscopy, dynamic grating techniques. Annotation copyright Book News, Inc. Por

Abstract: Summary of Band Gaps Measured for Various Compounds in This Studya The Journal of Physical Chemistty, Vol. 86, No. 4, 1982 467 sitions to a pseudo-two-dimensional system with d-d transitions. It is unclear whether the parabolic band as- sumption which is used in the three-dimensional materials is valid for these systems.lg The angle of incidence and the polarization of the in- cident light were varied in hopes that the change in the electric vector of the incoming radiation would couple the radiation more or less to the electronic transitions in the layered compound. Gerischer has observed an effect of the polarization and the angle of incidence on the photo- current spectxa of GazSePm The angular dependence was studied for p-polarized light with a normalization to s- polarized light at normal incidence for several doping levels in the semiconductor. The large angular dependences that were observed were explained by a large anisotropy in the absorption coefficient and by different diffusion lengths associated with the impurity doping. We were unable to measure significant changes in the photocurrent spectra as a function of the polarization

Abstract: The study of i.r. lattice vibrational bands (400–1200cm–1) for different types of zeolites with different particle sizes indicates, when synthesising a ZSM-type zeolite, that (i) the presence of a band at ca. 550 cm–1 in addition to the one at 450 cm–1 shows that ZSM-type zeolite, crystallites may have been formed, even if X-ray diffraction shows nothing, and (ii) the absence of the 550cm–1 band unambiguously shows that such a zeolite has not been formed.

Abstract: Quantization of Energy. Interaction of Electromagnetic Radiation with Atoms and Molecules. General Experimental Methods. Rotational Spectroscopy. Vibrational Spectroscopy. Electronic Spectroscopy. Photoelectron Spectroscopy. Lasers and Laser Spectroscopy. Appendix. References. Indexes.

Abstract: Characteristic features of photochemical hole-burning (PHB) in the impurity spectra of low-temperature solids and PHB applications in molecular spectroscopy are considered. The evolution of a no-phonon hole and a phonon sidehole in excitation and fluorescence spectra is analysed on the basis of model calculations. Some more complex models for PHB are considered, which take into account reverse reactions, the optical thickness of the sample, the inhomogeneous dispersion of both homogeneous linewidths and transition energies of the photoproduct and quasi-static impurity-impurity interactions. The effects of PHB on fluorescence line narrowing are discussed. By PHB homogeneous linewidths of purely electronic and vibronic no-phonon lines in the spectra of some porphine and phthalocyanine derivatives in various matrices are measured and their temperature dependence is studied. The latter is found to be essentially different in polycrystalline and glassy matrices. Line-broadening mechanisms are discussed. By PHB the existence of an inhomogeneous distribution of vibrational frequencies in molecular impurities is established. The applications of PHB in the studies of photochemical reactions in solid solutions of phthalocyanine derivatives and tetracene are regarded and the mechanisms of these reactions are discussed. The results obtained by PHB for chlorophyll and its derivatives are presented.

Abstract: A brief survey of some applications of beam-foil spectroscopy is presented. Among the topics covered are lifetime and magnetic moment measurements, nuclear alignment, and polarized light production. (AIP)

Abstract: The v2 = 1←0, 2←1, and 3←2 bands of the methyl radical were observed in the gas phase by infrared tunable diode laser spectroscopy at 606.4531, 681.6369, and 731.0757 cm−1. The observed vibration–rotation spectra were analyzed to derive precise values for the rotational constants, centrifugal distortion constants, and spin–rotation interaction constants. The absence of N = odd, K = 0 levels in the v2 = even states and of N = even, K = 0 levels in the v2 = odd states was confirmed, indicating that each vibrational state is nondegenerate. The observed band origins, when analyzed, led to a potential function for the out‐of‐plane bending vibration that has no potential hump at the planar configuration. The large negative anharmonicity of this potential was ascribed to a vibronic interaction with excited electronic states. The methyl radical was generated by a 60 Hz discharge in di‐tert‐butyl peroxide and was found to have a lifetime of about 1.4 msec; its concentration in the absorption cell was estimated to ...

Abstract: The aim of this series is to record the progress achieved each year in atomic and molecular spectroscopy due primarily to the introduction of laser spectroscopy. Topics covered in this volume include Electronic Excitations, Solutions, Solids, Surfaces, Metal Clusters and Counterions, Combustion Dynamics, Intramolecular Relaxation, Photochemistry and Photodissociation and Laser Surgery. They are studied by such techniques as Resonance Raman, Inverse Raman and Raman Gain Spectroscopy, Visible Overtone Spectroscopy and Multiphoton Spectroscopy. The concept for the series was developed from the symposia "Recent Advances in Laser Spectroscopy", held annually at the Polytechnic Institute of New York and organized by the Editors. However, whilst contributions are based upon the proceedings of these symposia, they are not restricted to that forum but include other useful and relevant additions.

Abstract: New spectroscopic evidence concerning the dynamics of electron-induced solvation clusters in polar liquids is presented and integrated with previous picosecond data, in order to outline the roles molecular dynamics and structure can play both in initiating electron localization at subpicosecond times and in governing the solvation dynamics to form e/sup -//sub s/ in the picosecond domain. Particulr emphasis is placed on the picosecond time-resolved absorption spectroscopy of electrons in a wide range of alcohols and alcohol-alkane systems at 300/sup 0/K as a framework for the cluster model of electron solvation. While the configurationally relaxed final quantum state of e/sup -//sub s/ appears identical for e/sup -//sub s/ generated by different techniques, it is possible that the time evolution of the solvation cluster and the dynamics of electron populations between localized and continuum states could be influenced by the initial state of the system. Selected examples are discussed for alcohols, amines, and water, and comparisons are made for picosecond observations from different visible and IR spectroscopic techniques, NMR, and complementary nanosecond electron mobility data to demonstrate the overall consistency of a model in which only the dynamical, microscopic properties of the liquid determine these solvation events.

Abstract: We have demonstrated rapid (3000 A/min) photochemical deposition of silicon dioxide from gas phase donor molecules An ArF (193 nm) laser was used to excite and dissociate gas phase SiH4 and N2O molecules in contrast to earlier work with incoherent mercury lamps We have achieved 20 times the deposition rate, limited the dissociation volume to a localized region, and minimized the direct impingement of UV photons on the substrate Although the SiO2 deposition rate was insensitive to substrate temperature from 20 to 600 °C, film quality noticeably improved above 200 °C Metal‐oxide‐semiconductor capacitors were fabricated and characterized in order to measure SiO2 electrical properties Film composition was investigated using Auger and infrared spectroscopy techniques and showed that the SiO2 is stoichiometric and contains less than 5% nitrogen

Abstract: A newly constructed crossed molecular beam apparatus and tunable infrared laser system is described. The Doppler effect has been used to measure the narrow velocity distribution in a molecular beam formed from a free jet expansion and to study the translational relaxation which occurs downstream of the nozzle orifice. In addition a laser-crossed molecular beam experiment is described which is designed to measure the rotational and vibrational state dependence of the total scattering cross section of hydrogen fluoride with helium.

Abstract: The 3p (3)P state of O and the 2s(2)2p(2)3p (4)D(0) states of N are populated by two-photon absorption at 226 and 211 nm, respectively, and the resulting near-IR fluorescence is detected. The exciting photons are provided by stimulated Raman frequency shifting, and the experiments are performed in a flow discharge. The measured lifetime of 39 (0) and 27 (N) nsec and quenching rate constants of 2.5 x 10(-10) cm(-3) sec(-1) for collisions of N(2) with each atom indicate promise for this method as a diagnostic tool in flames and plasmas.

Abstract: Laser induced fluorescence Doppler spectroscopy has been applied for the first time to atomic hydrogen using tunable VUV light at the Lyman-α line. The dissociation of HI at 266 nm into H+I(P 1/2) and H+I(P 3/2) has been investigated. The recoil energy, angular distribution and branching ratio of the H atom have been measured, serving to test and study the feasibility and applicability of the technique.

Abstract: The overtone spectra of the C–H stretching vibrations of several gaseous alkanes and alkenes were observed using laser photoacoustic spectroscopy. Resolvable peaks are seen for each chemically or sterically equivalent C–H bond and are assigned using the local mode model. The fifth overtone transition energies decrease linearly with increasing C–H bond lengths. Spectral shifts corresponding to 0.001 A bond length differences are observed. Linear correlations of bond length and anharmonicity with fundamental C–H stretching frequency allow a Morse potential for CH bonds to be defined in terms of a single parameter. The integrated cross section per C–H oscillator for the fifth overtone spectra varied mostly within a factor of 2 about the average value of (1.08±0.28)×10−23 cm2 cm−1.

Abstract: It is possible, by using Fourier-transform infrared (FTIR) difference spectroscopy, to detect the conformational changes occurring in both the protein and the chromophore of bacteriorhodopsin during the photocycle. In contrast to Raman spectroscopy, a laser is unnecessary and hence the problem of a perturbing probe beam is eliminated. Furthermore, the relatively high signal-to-noise ratio obtainable with FTIR enables measurements to be made in minutes over a large spectral range. In the study reported in this paper, we used this method to examine the state of protonation of the retinylidene Schiff base in light-adapted bR570 and in K, the first intermediate in the photocycle. Resonance Raman spectroscopy provides evidence that bR570 is protonated, but these results have been questioned on the basis of theoretical and experimental grounds. FTIR difference spectral changes in the bR570-to-K transition clearly indicate that bR570 contains a protonated Schiff base. In contrast, the K intermediate displays a Schiff base that is altered but still is associated to some degree with a proton. Because the low-temperature FTIR difference spectrum of bR570 and K is similar to the recently reported low-temperature resonance Raman spectra of bR570 and K [Braiman, M. & Mathies, R. (1982) Proc. Natl. Acad. Sci. USA 79, 403-407], we can assign most, but not all, vibrational changes in the bR570-to-K transition to the chromophore. These results are consistent with a simple model of the first step in the photocycle which involves a movement of the Schiff base proton away from a counterion.

Abstract: The stability of the ammonium radical (NH4) was determined from measurements of the kinetic energy released in its fragmentation products following formation in a fast electron capture process: NH4++Na → NH4*+Na+. Scattering profiles for heavy (NH3) and light (H) dissociation products were obtained from beam measurements with 5–16 keV NH4+ ions. The existence of a predissociative barrier in the radical is inferred from edge structure and scattering continua in H atom profiles. The radical is bound with respect to a potential minimum but all of the isotopic species NH4, NH3D, NH2D2, and NHD3 undergo rapid loss of H atoms and have ground states lying above their dissociation limits. The radical ND4 has unusual stability with its ground state lying close to or below its dissociation limit. Dissociative lifetimes for stable and unstable states of ND4 differ by at least two orders of magnitude. The possible significance of these observations on the interpretation of optical transitions involving the ground sta...

Abstract: The oxidation of UO/sub 2/ at 298 K has been studied by using X-ray photoelectron spectroscopy with a view to the characterization of U 4f shake-up satellites as a possible monitor of surface composition. On oxidation of U 4f shake-up satellite positioned at 8.2 eV to the high binding energy side of the U 4f/sub 5/2,7/2/ peaks is observed to grow progressively. It is proposed that this satellite is associated with the presence of anion defect clusters in UO/sub 2+x/.