Abstract: The inelastic tunneling of electrons in a metal-insulator-metal junction has been shown to be a spectroscopic method for studying the vibrational modes of the whole system. In the present paper we consider the possibility of deducing precise information from this spectroscopy. The low-voltage part of the spectrum (i.e., the $\frac{{d}^{2}I}{d{V}^{2}}\ensuremath{-}\mathrm{v}\mathrm{s}\ensuremath{-}V$ characteristic) gives information about the phonons of the electrodes. The phonon density, which is deduced for a Mg electrode, is critically compared with the density deduced from neutron scattering. The range of this phonon probe is then studied by tunneling into multilayer electrodes. The 40-90-meV range of the characteristic of a Mg-Pb junction exhibits a specific structure due to the lattice vibrations of the insulator. This structure is compared with the infrared spectrum and the phonon density of states of MgO, as well as with a theoretical calculation of the tunneling current in the transfer-Hamiltonian formalism. From the fit obtained, it is deduced that the 30-\AA{}-thick insulator, grown on Mg, is an oxide, in contrast with the insulator grown on Al, which was previously deduced to be a hydroxide. At higher energies (100-500 meV), the vibrational spectrum of molecules contained in the insulator region is observed. The identification of the lines is shown to be accurate and it gives precise information on these molecules, especially about their chemical binding with the insulator. This last point could be important in the future for studying the problem of adsorption on solid surfaces.

Abstract: Surface-state transitions on ordered silicon (100)2 x 1 and (111)7 x 7 surfaces have been observed by electron energy-loss spectroscopy. The surface transitions were identified by comparing the clean ordered surfaces with clean disordered surfaces, and with disordered surfaces due to submonolayer quantities of absorbed oxygen. Three transitions are observed corresponding to surface states near the top, near the middle, and at the bottom of the valence band. These surface-state transitions are stronger on the (111)-7 x 7 surface than on the (100)2 x 1 surface. (auth)

Abstract: A new technique for performing optical spectroscopy on solids has been developed Photoacoustic spectra of cytochrome c and hemoglobin show how this technique can be used to obtain information about optical absorptions and subsequent de-excitations in solid biological materials, particularly those which cannot readily be studied by conventional means

Abstract: — Optical absorption and emission spectra of retinal, axerophtene, anhydrovitamin A, and 2,10-dimethylundecapentaene in rigid glass matrixes at 77°K are presented. An interpretation of the observed spectra which provides a rationalization on the basis of electronic structure for the diffuse nature of the retinal spectrum is discussed. For the undecapentaene a weakly absorbing 1Ag state was found 3250 cm-1 lower in energy than the level responsible for the strong visible absorption.

Abstract: The polarity of a number of loosely bound complexes is qualitatively measured by molecular beam electric deflection. The following species are observed as polar: ArNO, ArHCl, NeDCl, XeHCl. ArBF/sub 3/, KrBF/sub 3/, (NO)/sub 2/, (HCl)/sub 2/, BF/sub 3/NO, BF/sub 3/CO, (CO/sub 2/)/sub 2/, Among the species observed to be nonpolar are: (NO)/sub 3/, (NO)/sub 4/, N/sub 2/0/sub 2/, NeHCl, COH/sub 2/, (BF/sub 3)/sub 3/, (BF/sub 3/)/sub 4/, (BF/ sub 3/)/sub 4/. Structural interpretations of these results, together with some preliminary radiofrequency spectroscopy, are presented.

Abstract: Fluorescence lifetimes of low pressure gaseous systems are necessary for the understanding of electronic relaxation in an isolated molecule. A detailed experimental and theoretical analysis of the technique of single photon decay spectroscopy is presented. This includes the construction of nanosecond light sources, the detection and timing of single photons, and a statistical analysis of the results. Standards for time calibration and detection sensitivity are suggested. This paper provides the basis for subsequent studies of the fluorescence decay of aromatic vapours.

Abstract: Publisher Summary This chapter discusses new techniques and applications of ultraviolet difference spectroscopy Ultraviolet techniques currently in use or being developed can be roughly classified as (1) those in which the changes in the spectra of chromophores are observed under the dynamic conditions of biological interest (eg, change of pH, state of aggregation, conformation, interaction with substrate or inhibitor) and (2) those in which a change is introduced by the experimenter under static conditions—those for which the conformation or degree of aggregation of the protein remains constant These latter techniques can all roughly be classified together as “spectral perturbation” techniques Perturbations may be produced by nearly any physical or chemical means—for example, alteration of pH, temperature, pressure, or solvent composition—and are generally useful for the study of the protein in its native conformation

Abstract: A tunable, single frequency, continuous wave, dye laser has been used to optically pump various lines of the BaO A 1Σ‐X 1Σ electronic transition. Microwave optical double resonance (MODR) spectra are recorded as changes in the intensity of dye laser induced photoluminescence. Fourteen microwave rotational transitions in the X 1Σ (ν = 0,1) and A 1Σ (ν = 0–5) states of 138Ba16O and one transition in the A 1Σ (ν = 1) state of 137Ba16O have been observed. Partially deperturbed rotational constants obtained for BaO A 1Σ are B(ν) = 0.25832(2) − 0.001070(5) (ν + 1/2) cm−1. Two physical models are described which account for microwave optical double resonance effects in the strong (nonlinear) and weak (linear) optical pumping limits. Observed changes in photoluminescence polarization caused by excited state microwave transitions are predicted by a semiclassical transition dipole model. A three level steady state kinetic treatment of microwave optical double resonance indicates that the BaO MODR transitions reported in this paper are observed near the strong optical pumping limit. It is shown that for most allowed transitions in diatomic molecules a 100 mW single frequency, dye laser is sufficiently intense to significantly deplete rotational levels of the electronic ground state with respect to neighboring rotational levels and to cause the populations of the depleted ground state and optically pumped excited state levels to become comparable.

Abstract: We have utilized the techniques of picosecond spectroscopy to study the localization of an excess electron in water. Quasifree electrons were generated by the photoionization of the ferrocyanide anion in aqueous solutions at 2650 A. Time resolved absorption of the localized electron was monitored continuously from 1.06 μ to 5300 A, while time and energy resolved absorption was monitored in the range 3100–9000 A by a broad continuum of picosecond duration. Optical absorption of the initially localized electron in the infrared (1.06 μ) is observed within 2 psec after the generation of the quasifree electron. The optical absorption band evolves in time, shifting from lower to higher energies, and the ``normal'' absorption of the hydrated electron is developed in ∼4 psec.

Abstract: Resonance Raman spectra have been obained from various iodine solutions. High intensity overtone progressions of the stretching vibration were observed, allowing the determination of the spectroscopy constants ωe and ωexe and estimation of ωeye for the stretching vibration for the ground state in various environments. The values are compared to those obtained for the gas phase. The overtone progression shows a large increase in half-bandwidth with increasing vibrational quantum number.

Abstract: A simple technique is described which makes it possible to record Raman difference spectra of binary liquid systems. The main feature is a divided rotating Raman cell for liquids and a gated electronic system. The cancellation of solvent lines in the Raman spectrum of a solution is demonstrated on a 1:1 mixture of CCl4 and CHCl3 and on an MnO4−-H2O solution. Further advantages of this technique are accurate wavenumber shift measurements (e.g., the isotopic lines of ν1 in CHCl3) and correction of the intensity error of Raman lines obtained from highly absorbing solutions (e.g., I2-CHCl3).

Abstract: Laser-induced fluorescence line narrowing has been studied in a series of samples of glass: Nd. The features of the nonresonant-excitation technique are described, and the results are discussed in terms of the known spectroscopic properties of the glass: Nd system. The concentration and temperature dependence of the line narrowing have been studied, and the spectral diffusion that is observed is analyzed in terms of resonant ion-ion energy transfer.

Abstract: Energy-level spectra obtained for the (111), (110), and (100) faces of Si and Ge by ion-neutralization spectroscopy (INS) bear only a superficial resemblance to the bulk density of states for these solids. In particular, the energies of small peaks in the INS-unfold function vary from one surface to another, and also differ from the energies of bulk critical points determined either by theory or by spectroscopies which more nearly yield bulk properties. A similar statement can be made for the width of the degenerate $p$ band, which is narrower at the surface as revealed by INS than it is in the bulk. Thus, the principal conclusion of this paper is that the local density of states (density of states weighted by local-wave-function magnitude) is significantly modulated as one proceeds from the bulk of a solid to its surface. The surface state observed for Si(111) by photoemission as overlapping the top of the valence band is seen in the INS spectra for both the Si(111)1 and Si(111)7 surfaces. The INS spectra for other Si surfaces and for all of the Ge surfaces studied do not show the kind of definitive evidence for a surface state seen in the Si(111) data although we cannot say that such surface states are not present with reduced intensity.

Abstract: ESR experiments with time resolution on the order of 1 μsec have been carried out upon aqueous solutions during repetitive pulse radiolysis with a 2.8 MeV electron beam. The ESR spectrometer was operated with no field modulation, and spectra were presented as absorption curves. The radicals ĊH(CO2−)2, ĊH2CO2−, and hydroxycyclohexadienyl, formed in each case by reactions of OH, were studied and each spectrum showed evidence of a nonequilibrium population of spin levels, with the low field lines of the latter two radicals observed in emission. For ĊH2CO2− this emission persists for ∼ 50 μsec. The observed signals are described by enhancement factors V (fractional excess signal) of 0.23, 3.1, and 12.3, respectively. From the short spin relaxation times (1.4 μsec was measured for ĊH2CO2−) it is evident that emission existing at times much greater than this relaxation period must be the result of a continuous regeneration of the population differences by the radical‐radical reactions. The form of the kinetic e...

Abstract: The hyperfine splittings of the Na D1 and D2 lines were investigated using a single mode cw dye laser. The light of the laser was scattered by the atoms of an atomic beam and the fluorescent light was observed as the frequency of the laser was tuned across the D lines. The Doppler width of the atomic beam was reduced to about 2.5 MHz so that the absorption width of the atoms of the beam was essentially determined by the natural width of the 32P1/2 and 32P3/2 levels, which is about 10 MHz. Since the linewidth observed for the hyperfine transitions was 30 MHz, most of the hyperfine components of the D1 and D2 lines could be resolved. In another experiment the frequency of the dye laser was locked to a hyperfine transition of the D1 line. The observed variation of the output frequency of the dye laser was less than ±1.5 MHz. In addition, the intensity of the dye laser was controlled to about 10−3, using an electro-optically variable transmission filter.

Abstract: In both fundamental and applied surface physics, it is essential to know as much as possible about the chemical composition of the outer atomic layers of solids. Rapid progress has recently been made in the development of analytical methods which could be used in surface analysis. All utilize some type of emission (photons, electrons, atoms, molecules, ions), caused by excitation of the surface states. Both the “excitation” and emission processes must meet certain basic requirements as regards information depth, form in which the information is obtained, sensitivity, changes in the surface layer during analysis, etc. The more important of the methods that qualify, namely Auger-Electron Spectroscopy (AES), photo-Electron Spectroscopy for Chemical Analysis (ESCA) and the static method of Secondary-Ion Mass Spectrometry (SIMS), are discussed and their potentialities and limitations illustrated by characteristic examples.

Abstract: Measurement of the absolute cross sections for the excitation of a number of N I multiplets by electron impact on atomic nitrogen. Two of these cross sections - 1134 and 1200 A - are found to be large, reaching 2.0 x 10 to the minus 16th and 2.5 x 10 to the minus 16th sq cm at their peaks, respectively. The presence of vibrationally excited molecular nitrogen in the discharged gas is confirmed, and its effect on the measurements is discussed. The ratio of the oscillator strengths of the 1200- and 1134-A resonance transitions is measured to be 2.6 plus or minus 0.3.

Abstract: Nuclear magnetic resonance spectroscopy has been widely used in recent years to investigate the kinetics of chemical reactions. Dynamic nuclear magnetic resonance spectroscopy covers the investigation of temperature-dependent n.m.r. spectra and the calculation of rate constants and Arrhenius parameters from these spectra. The present Review describes the principles of d.n.m.r. spectroscopy, methods of recording the spectra, and their processing by exact and approximate methods. The theoretical and experimental foundations are illustrated by many examples of the investigation of hindered rotations, inversions, and rearrangements in various organic and organometallic systems. A list of 81 references is included.

Abstract: Relaxation of the population distribution of electronic states is studied theoretically for a highly ionized nitrogen-hydrogen mixture expanding through a nozzle wherein the hydrogen content is less than 0.1%. The analysis incorporates quantum-mechanical rate coefficients, and considers the effects of wall cooling and absorption of radiation. Calculations are carried out for a condition produced experimentally. Visible and infrared line radiations from nitrogen and hydrogen were measured with a spectrograph. The geometry and stagnation conditions were those calculated theoretically. The experiment confirms quantitatively the predictions that the electronic excitation temperatures of hydrogen and (3P) core states of nitrogen are higher than the electron temperature, and that (3P) excitation temperatures exhibit maxima within the nozzle.

Abstract: A table of wavelengths, statistical weights, and excitation energies is given for 944 atomic spectral lines in 221 multiplets whose lower energy levels lie below 0.275 eV. Oscillator strengths were adopted for 635 lines in 155 multiplets from the available experimental and theoretical determinations. Radiation damping constants also were derived for most of these lines. This table contains the lines most likely to be observed in absorption in interstellar clouds, circumstellar shells, and the clouds in the direction of quasars where neither the particle density nor the radiation density is high enough to populate the higher levels. All ions of all elements from hydrogen to zinc are included which have resonance lines longward of 912 A, although a number of weaker lines of neutrals and first ions have been omitted.

Abstract: The properties of all $f\ensuremath{-}p$-shell nuclei with $42\ensuremath{\le}A\ensuremath{\le}44$ have been calculated from one consistent shell model. The model space includes all Pauli-allowed states for all configurations of two, three, or four particles distributed among the four $f\ensuremath{-}p$ shell orbits. The model Hamiltonian is a one-body plus two-body operator very similar to the "realistic" effective Hamiltonian of Kuo and Brown. Calculated results are given for excitation energies, single-particle transfer spectroscopic factors, electric-quadrupole and magnetic dipole moments, and $B(M1)$'s and $B(E2)$'s for transitions between low-lying states. The calculated results are in fair agreement with experimental information on these various observables. The results suggest that core-excitation effects are more important in the lower half of the ${f}_{\frac{7}{2}}$ shell than in the $s\ensuremath{-}d$ shell.