Abstract: Visible (red) absorption spectra of benzene (h6 and d6), methyl substituted benzenes, naphthalene, and anthracene are presented as seen by thermal lensing spectroscopy. It is shown how this highly sensitive laser‐based technique can easily detect transitions having absorption coefficients as small as 10−6 cm−1. The observed transitions are principally due to C–H stretching vibrations at the sixth quantum of excitation. The local mode (LM) model for describing such molecular states is explored in some detail with reference to the C–H excitations in benzene. Based on a two parameter empirical fit, the LM model can give a true C–H stretch ’’mechanical’’ frequency; it successfully predicts isotope effects; and it fully determines the energy level scheme at any quantum of excitation. The LM energy level scheme for the 462 C–H stretching states at the sixth quantum of excitation is presented. A majority of these states are only mildly anharmonic; one state in fact is a perfect harmonic of the fundamental. However, only the most anharmonic state of the 462 is the spectroscopically allowed one. The LM model, already introduced in the literature, is seen to be an excellent zeroth order description of those very same highly excited vibrational states most readily accessible to a sensitive absorption technique such as that offered by the thermal lensing effect.

Abstract: We describe an automatic fringe‐counting interferometer with real‐time wavelength readout for cw laser sources. Sub‐Doppler absolute wavelength accuracy (∼2×10−7) is demonstrated with saturated absorption spectroscopy in neon.

Abstract: Both a single beam and a dual beam (with synchronous detection) thermal lens technique have been employed in the measurement of "colorless" organic compounds in the range 15,700 to 17,400 cm-1 Combination overtones of C-H stretching vibrations in benzene have been identified and agree with previous results obtained by conventional spectroscopy with a long optical path Extinction coefficients as low as 1 X 10(-6) liter mole-1 cm-1 have been accurately determined The sensitivity of the technique has been further demonstrated by measuring the So leads to T1 absorption of anthracene; the spectrum compares favorably with results obtained by conventional techniques

Abstract: Atomic and molecular spectroscopy with lasers.- Infrared spectroscopy with tunable lasers.- Double-resonance spectroscopy of molecules by means of lasers.- Laser Raman spectroscopy of gases.- Linear and nonlinear phenomena in laser optical pumping.- Laser frequency measurements, the speed of light, and the meter.

Abstract: Photoemission studies of valence bands, core levels, empty surface states, and band bending for cleaved GaAs (110) are described. These studies show that there are no intrinsic band‐gap surface states for GaAs (110), and that large (approx. greater than 0.5 eV) excitronic binding energies are involved in core‐level‐to‐empty‐surface‐state transitions (e.g., using yield spectroscopy or electron energy‐loss spectroscopy). Studies of the effects on chemisorbed oxygen and thin Au overlayers on InAs (110) and GaAs (110) surfaces are also described. Trends and correlations in III–V semiconductor empty surface states are discussed.

Abstract: The quenching of the charge-transfer excited states of Ru(bpy)/sub 3//sup 2 +/ and Os(bpy)/sub 3//sup 2 +/ by O/sub 2/, Fe/sup 3 +/, Co(phen)/sub 3//sup 3 +/, Ry(NH/sub 3/)/sub 6//sup 3 +/, Os(bpy)/sub 3//sup 3 +/, and Fe(CN)/sub 6//sup 3 +/ has been studied by a spectrofluorometric method. The lifetime of the emitting state of the osmium (II) complex and the rate of its reaction with Ru(NH/sub 3/)/sub 6//sup 3 +/ were measured by a single-photon counting technique. A value of -0.96 V was estimated for the reduction potential of the Os(bpy)/sub 3//sup 3 +/ parallel *Os(bpy)/sub 3//sup 2 +/ couple. Emission intensity measurements were used to determine the steady-state concentrations of the Fe/sup 2 +/ and Ru(bpy)/sub 3//sup 3 +/ formed in the reaction of Fe/sup 3 +/ with the emitting state of Ru(bpy)/sub 3//sup 2 +/. The steady-state concentrations of the electron-transfer products increase in the order HCl < H/sub 2/SO/sub 4/ < HClO/sub 4/ approx. CF/sub 3/SO/sub 3/H and in 0.5 M HClO/sub 4/ amount to about 25 percent of the initial Ru(bpy)/sub 3//sup 2 +/ concentration under the conditions used. The Ru(bpy)/sub 3//sup 2 +/-Fe/sup 3 +/ system exhibits a large photogalvanic effect. The mechanisms ofmore » the reactions are discussed and general equations describing the steady-state characteristics of these systems are derived. (auth)« less

Abstract: HeI induced valence electron spectra of benzene and the hexafluorides of sulphur, molybdenum, tungsten and uranium are presented together with a HeII spectrum of sulphur hexafluoride. Vibrational band structure has been resolved in the spectra of all molecules and the energies of these bands are reported. A description is also given of the multichannel detector system which has facilitated the recordings of these spectra.

Abstract: A significantly increased resolution in the proton-coupled 13C NMR spectrum of MeI was achieved by 2-dimensional J spectroscopy. [on SciFinder (R)]

Abstract: Laser-Raman spectroscopy is largely complementary to ir spectroscopy, but spectral interpretation is simpler. Lack of homogeneity in clinker minerals, direct study of white portland cement hydration, characterization of clinker minerals, identification of the various calcium sulfate forms, and effects of carbonation are discussed.

Abstract: The structure of the complex formed between HF and ClF has been determined by molecular beam electric resonance spectroscopy. The molecule HFClF is a slightly asymmetric prolate top. The spectroscopic constants determined from K=0 spectra of several isotopic species are as follows: The atomic arrangement in the complex is HFClF with the three heavy atoms collinear. The proton is off axis by 55°. The FCl van der Waals bond length is 2.76 A. Comparison of the structure of HFClF with that of (HF)2 shows striking similarities. It appears that the bonding in both complexes is quite similar.

Abstract: A spectroscopic method is developed in which the frequency of microwave radiation is added to or subtracted from that of infrared radiation by using two-photon processes in molecules. By utilizing many lines of the C${\mathrm{O}}_{2}$ and ${\mathrm{N}}_{2}$O lasers, this method enables us to perform systematic high-resolution spectroscopy in the 10-\ensuremath{\mu}m region. Both straightforward two-photon absorption spectroscopy and two-photon Lamb-dip spectroscopy can be used. We describe the theory of this method and its application to the observation of the ${\ensuremath{ u}}_{2}$ band of $^{14}\mathrm{N}$${\mathrm{H}}_{3}$ and $^{15}\mathrm{N}$${\mathrm{H}}_{3}$.

Abstract: The effect of multiplexing in Fourier transform spectroscopy (FTS) (and other coding techniques such as Hadamard transform spectroscopy) on the signal/noise ratio arises from two factors. The first of these is a N½ improvement for a spectrum containing N resolution elements since each individual resolution element is now viewed for an N-fold longer time. The second factor is due to the simultaneous observation of all resolution elements, raising the signal level by a factor N for an uniform spectrum.

Abstract: Highly resolved rotational spectra of two‐photon excited vibrational levels in the 1B2u state of C6H6 and C6D6 are recorded for linear and circular polarization of the exciting laser radiation, generated with a powerful narrow‐band dye laser system. The fitted theoretical spectra are in excellent agreement with the experimental results and provide molecular parameters (rotational constants, Coriolis constants, and structural parameters) of considerably improved accuracy.

Abstract: We investigate spectral changes induced by high-power CO 2 laser radiation in the direct intervalence band absorption of p-type germanium. Using a model of inhomogeneously broadened two-level systems, we deduce a room-temperature saturation intensity of 4 MW/ cm2from published observations of saturation of this absorption. The applicability of the two-level model to transitions between two electronic bands is discussed. We relate the linear absorption coefficient to the saturation intensity and the effective population difference, where the latter is obtained in a spherical band approximation. The result yields a value of 0.55 ps for the geometric mean of the phase and energy relaxation times. The meaning of these times is explained for our system, and quantitative agreement is found with published data on optical and acoustical lattice scattering probabilities. Specifically, we find a very short phase relaxation time of 0.09 ps. This allows the prediction of a burnt-hole spectral width of 57 cm-1(HWHM) at small saturation. In a preliminary experiment, we have observed the modulation of a CW CO2laser beam by intense nanosecond pulses of a second CO2laser offset in frequency by up to 140 cm-1.

Abstract: A systematic investigation of the fine structure of adsorbate peaks in Auger spectra is presented. Spectra of a wide range of systems involving carbon, sulphur, oxygen, chlorine, and nitrogen adsorbates on copper, nickel, iron, and zinc substrates are reported with a resolution $\frac{\ensuremath{\Delta}E}{E}\ensuremath{\sim}0.006$. According to a previous suggestion two types of transitions are identified and separated in such spectra. Interatomic transitions involve deexcitation of the initial adsorbate core hole from electrons in the substrate valence band. These transitions are rather similar to the ones involved in ion neutralization spectroscopy and are relatively unperturbed by final-state effects. Intra-atomic transitions show the same type of perturbation already observed in other investigations of Auger spectra involving rather localized valence bands, like $d$ bands in transition metals. We identify peaks associated to spectral terms corresponding to final-state configuration interaction. Measurements of the energy of these peaks are used, in connection with photoemission binding energies of other authors, for calculating energy shifts. These shifts are then tentatively analyzed in terms of relaxation energies and, particular, extra-atomic relaxation energies are estimated. A discussion of the general conditions for correlating Auger-electron data and valence-band density of states is offered.

Abstract: Coherent anti-Stokes Raman scattering (CARS) spectra have been obtained for ferrocytochrome c and cyano cobalamin in aqueous solution at millimolar concentrations, using a pair of tunable dye lasers pumped by a pulsed nitrogen laser. Resonance enhancement was obtained by tuning the omega1 laser to the visible absorption bands of the samples. The spectral features correspond to those observed in the conventional resonance Raman spectra. It appears that CARS spectroscopy, with its advantageous fluorescence rejection, can be usefully applied to biological samples by exploiting resonance enhancement. While the background scattering from water is 10 times higher than that of benzene and other aromatic solvents, it is actually at the low end of the scale for most liquids. The anomalously low background of aromatic liquids is thought to result from competition by the unusually efficient stimulated Raman scattering which they display. Off-resonance spectra for both cobalamin and cytochrome c contain negative peaks, i.e., absorption bands in the background. These are interpreted as inverse Raman processes induced by the omega1 photons in the presence of the continuum provided by the background scattering. While both CARS and the inverse Raman effect are subject to resonance enhancement, the wavelength dependence of CARS is evidently steeper.

Abstract: Ten pure rotational Q-branch transitions of the distortion moment spectrum of GeH4 have been measured between 9 and 23 GHz. They were observed in a conventional Stark modulated spectrometer modified to have a sensitivity of 1 × 10−11 cm−1. No Ge isotope splitting was observed in the spectrum. The spectrum was analysed in terms of a single set of six tensor centrifugal distortion constants DT, H4T, H6T, L4T, L6T, and L8T. The results were found to predict accurately transitions previously reported from infrared–microwave double resonance spectroscopy, and a complete analysis using both sets of data was carried out. The results are (in hertz): DT = 67 775.54 ± 0.86; H4T = −5.3827 ± 0.0055; H6T = 2.9693 ± 0.0019; L4T = (3.996 ± 0.088) × 10−4; L6T = −(4.122 ± 0.050) × 10−4; L8T = −(8.01 ± 0.14) × 10−4. The errors here are the standard deviations obtained from the least-squares analysis; estimates of the absolute errors are also given. For possible application in other high resolution studies, the constants ha...