Showing papers on "Resonance published in 1980"

Partially deuterated water dimers: Microwave spectra and structure

Abstract: Radio frequency and microwave spectra for various isotopically substituted water dimers have been studied by molecular beam electric resonance spectroscopy. Resolved radio frequency hyperfine transitions have provided information about the tunneling–rotational levels of water dimer. The microwave spectra have been analyzed with a rigid rotor model to give the following structural information: Roo=2.976 A (+0.000, −0.030 A), ϑd=−51(10)°, ϑa=57(10)° and χa=6(20)°. The effects of large amplitude vibrational motion have been estimated and the equilibrium geometry should lie within the above limits. The experimental data is also consistent with χa and φd equal to zero for the equilibrium geometry. The water dimer structure, therefore, has a symmetry plane, a trans configuration, and a linear hydrogen bond within quoted error limits.

Electron spin resonance studies of magnetic soliton defects in polyacetylene

Abstract: We present electron spin resonance studies of the magnetic defect in undoped polyacetylene. Temperature dependences of the absorption spectra of (CD)x and (CH)x over the range 2–295 K have been obtained. The properties of the magnetic defect in fully isomerized trans samples and in cis‐rich samples are compared. The data are consistent with a description in terms of a mobile neutral magnetic defect in the trans polymer and a stationary one in the cis‐rich polymer. The spin resonance linewidths are determined by unresolved hyperfine splittings resulting from interaction of the electron spin with many nuclear spins within the envelope of the spatially extended magnetic defect. The results of analyses of the detailed line shapes and linewidths are discussed in terms of the bond alternation domain wall (soliton) model of the magnetic defect.

Molecular spectra, Fermi resonances, and classical motion

Abstract: Classically periodic molecular vibration (such as a totally symmetric stretch) can be unstable against the addition of small components of other modes, depending on anharmonic coupling strengths, near resonance of fundamental frequencies, and the total energy. We report here on some very strong correspondances between classical stability of the motion and quantum spectral features, wave functions, and energy transfer. The usual concept of a vibrational Fermi resonance turns out to apply best to the case where the transition to classical instability occurs at an energy below the first resonant quantum levels (this is the case for the famous Fermi resonance in CO2). In the (probably more common) event that resonant classical instability should set in above several quanta of energy in the mode of interest, the quantum spectrum shows tell‐tale pre‐ and post‐resonant signatures which include attraction of quantum levels (rather than the usual Fermi repulsion) and other features not normally associated with Fer...

Saturation spectroscopy with laser optical pumping in atomic barium

Abstract: The magnitude and sign of laser saturation resonances induced in atomic transitions with level degeneracy can be dramatically altered by the presence of optical pumping. This paper presents a detailed theoretical treatment of optical-pumping Lamb dips and crossover resonances, and their experimental observation in the 553-nm barium resonance transition. The physical principles underlying the laser optical-pumping saturation effect are also discussed.

Resonance enhanced two-photon ionization studies in a supersonic molecular beam: Bromobenzene and iodobenzene

Abstract: The 1B2(ππ*)←1A1 absorptions of two monosubstituted halobenzenes have been investigated using resonance enhanced two‐photon ionization in a pulsed supersonic molecular beam. Detection of the photoions was accomplished by means of a time‐of‐flight mass spectrometer. The 1B2←1A1 system of bromobenzene has been observed with good sensitivity using this technique, even though the total decay rate of the 1B2 state is greater than 1×1011 sec−1. No ion signal was observed when the same transition was probed in iodobenzene, allowing us to place a lower limit on its decay rate of 4×1013 sec−1.

Surface-Enchanced Raman Scattering from Pyridine on Ag(111)

Abstract: This Letter reports the first ultrahigh-vacuum study of surface-enhanced Raman scattering from pyridine adsorbed on a clean single-crystal silver surface containing a smooth modulation (1 \ensuremath{\mu}m periodicity) to allow optical coupling to surface plasmon polaritons. A large mode-selective enhancement (\ensuremath{\sim}${10}^{4}$) of the Raman signal from the first monolayer is observed at surface-plasmon-polariton resonance. Coverages greater than one monolayer show a smaller enhancement (\ensuremath{\sim}${10}^{2}$).

Nuclear Antiferromagnetic Resonance in Solid He 3

Abstract: Detailed measurements of the low-field antiferromagnetic resonance spectrum of spin-ordered bcc 3He exhibit large shifts from the Larmor frequency, with a zero-field resonant frequency near zero temperature of Ω0/2π≃825 kHz. Analysis of the spectrum leads to stringent constraints on possible sublattice structures. The temperature dependence of Ω0 shows low-temperature behavior expected from spin-wave theory, and indicates a first-order transition at 1.03 mK.

High- Resolution Optical Spectra of Laser Cooled Ions

Abstract: We obtain essentially Doppler free spectra of the naturally occuring isotopes of Mg+, which are bound in a Penning trap, by using a frequency stabilized laser to continuously cool the ions, while the scatter rate from a second, frequency swept laser is, monitored. We show that the magnetron motion as well as the cyclotron and axial motion can be minimized. Line position measurements yielding resonance transition energy, isotope and hyperfine shifts are reported.

X‐ray photoelectron spectroscopy and paramagnetic resonance evidence for shock‐induced intramolecular bond breaking in some energetic solids

Abstract: Solid samples of 1,3,5, trinitro 1,3,5, triazacyclohexane (RDX), trinitrotoluene (TNT), and ammonium nitrate were subjected to shock pulses of strength and duration less than the threshold to cause detonation. The recovered shocked samples were studied by x‐ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). The results of these measurements indicate that the shock pulse either broke or altered the internal bonds of the molecules of the solid. The results of the shock decomposition are compared with measurements of the uv and slow thermal decomposition of these materials using the same experimental techniques.

Bimolecular Reactions of Vibrationally Excited Molecules

Abstract: ion reactions involving at least one species with an unpaired electron. As shown in Figure 8, the exoergic reaction between nitric oxide and ozone looks very interesting in this respect. The reaction proceeds by two parallel paths to yield ground-state vibrationally ex­ cited (A) and electronically excited (B) N02 molecules (178-180) NO + 03 � NOiCAI) + 02 £:=9.7 kJ mol-I E�= 17.5 kJ mol-I. The spacing of the three vibrational modes in 03 as well as the vibrational quantum in NO are comparable to the measured thermal activation energies. Both reactants can be vibrationally excited by molecular infrared lasers. For ozone a coincidence between the P(30) line of the CO2 laser in the 9.6 p.m band and the antisymmetric stretch vibration (001) exists. Nitric oxide has a near coincidence with the P(l3) line in the �v = 9-8 band at 5.3 /Lm of the CO laser. Because NO is a paramagnetic molecule, the NO absorption line can be "tuned" by a magnetic field (0.76 kG) in resonance with the laser line. Near-IR

The mathematical theory of resonances whose widths are exponentially small

Abstract: It is shown how the rigorous justification of resonance widths in Paper I [5] can be simplified by exploiting Langer's trick of expanding the independent variable rather than the dependent variable [9].

Di-iron and nickeliron

Abstract: Resonance Raman progressions assigned to Fe2 and NiFe isolated in solid Ar and Kr are reported. ωe″ and ωe″xe″ for the two molecules are found to be 299.6 and 1.4 cm−1 and 320.0 and 1.32 cm−1, respectively. In addition, an anti‐Stokes progression of inordinate intensity was observed for Fe2. On the basis of a laser power study this was suggested to arise from consecutive two‐photon absorption processes which are efficient in this case as a result of very long vibrational relaxation lifetimes of the excited vibrational states of the electronic ground state of Fe2. No spectrum of Fe2 was detected in either solid N2 or solid methane, supporting previous reports that Fe2 reacts with these substances to form complexes. With high resolution, each of the bands of the resonance Raman progression of Fe2 is observed to be a multiplet. Some of the multiplet structure results from the expected isotope effect but additional structure is seen because for a particular value of Δv″ there are transition with different ini...

Resonant modes of optical cavities with phase-conjugate mirrors.

Abstract: The lowest-order self-consistent Gaussian transverse modes are derived, also the resonant frequencies of an optical resonator formed by conventional paraxial optical components plus a phase-conjugate mirror (PCM) on one end. The conventional optical elements are described by an over-all ABCD matrix. Cavities with purely real elements (no aperturing) have a continuous set of self-reproducing Gaussian modes described by a semicircular locus in the 1/q plane for one round trip; all Gaussian beams are self-reproducing after two round trips. Complex ABCD matrices, such as are produced by Gaussian aperturing in the cavity, lead to unique self-consistent perturbation-stable Gaussian modes. The resonant frequency spectrum of a PCM cavity consists of a central resonance at the driving frequency omega(0) of the PCM element, independent of the cavity length L, plus half-axial sidebands spaced by Deltaomega(ax) = 2pi(c/4L), with phase and amplitude constraints on each pair of upper and lower sidebands.

A spherical-box approach to resonances

Abstract: It is shown that the energies and widths of resonances can be determined from the discrete states calculated in a spherical box. The variation of the radius of the box exhibits clearly the positions as well as the widths of the resonances. Two formulae are given to calculate the resonance width using only the energies of the discrete states as a function of the radius. The approach is exemplified by two model problems.

Theory of resonance-radiation pressure

Abstract: A general theory of the motion of a two-level atom in a resonant or near-resonant electromagnetic wave of arbitrary amplitude and phase, including effects of radiative relaxation due to interaction with the quantized vacuum field, is developed from first principles. Particular emphasis is placed on the effects of quantum-mechanical fluctuations of the radiation force and on the associated diffusion of atomic momentum due to spontaneous and induced absorption and emission processes. Analytic results and numerical examples are presented for (1) the lower bound on the temperature achievable by radiation cooling in a standing wave tuned below resonance, (2) the heating rate in a strong resonant standing wave, (3) the maximum confinement time for an atom in a Gaussian radiation trap, (4) the deflection and spreading of an atomic beam transversely illuminated by a strong resonant running wave, and (5) the transverse cooling of an atomic beam by a strong running wave tuned below resonance.

Resonance effects in low-loss ring waveguides

Abstract: Low-loss channel waveguides in a ring-resonator configuration have been fabricated; measured results show a finesse of 16 and a coupling efficiency of 2%. Total losses, including coupling, material, bending, and fabrication losses, were 0.05 ± 0.01 dB/cm.

Classification of the X-ray spectra of transitions in the Ne, F and O I isoelectronic sequences of the elements from iron to bromine and in the Na I isoelectronic sequence of gallium to bromine

Abstract: X-ray spectra of the elements iron to bromine have been observed from plasmas produced by the laser irradiation of plane solid targets. Observed wavelengths are classified as belonging to the Na, Ne, F and O I isoelectronic sequences. A comprehensive survey of the Ne-like transitions is given for these elements. Classifications are also given for the transitions 2s22p5-2s22p43s, 3d, 4s, 4d and 2s22p5-2s2p53p in the F I isoelectronic sequence and 2s22p4-2s22p33s, 3d, 4d in the O I isoelectronic sequence. Long-wavelength Na-like satellites to the Ne-like resonance lines are also classified for the elements gallium to bromine.

Observation of the Surface State Resonance Effect by the Convergent Beam RHEED Technique

Abstract: The angular dependence of the specular spot intensity reflected from a ZnS (110) surface has been analyzed by using Bethe's: dynamical theory. Many-beam calculations have been carried out with simple surface potential models. The calculations showed that the angular dependence of the intensity changed very sensitively with the surface potential shape at the surface state resonance positions. One of the models was in very good qualitative agreement with the present experimental result.

New giant resonances in 172-MeV. cap alpha. scattering from /sup 208/Pb

Abstract: Spectra of 172-MeV ..cap alpha.. scattering from /sup 208/Pb indicate in addition to giant monopole and quadrupole excitation new giant resonance structures in hadron scattering at E/sub x/=17.5 +- 0.8 and 21.3 +- 0.8 MeV with corresponding widths of 4.8 +- 0.8 and 5.9 +- 0.8 MeV. The angular distributions indicate L=3 and 1 giving rise to an interpretation as isoscalar giant octupole resonance (17.5 MeVm 60% energy-weighted sum-rule strength), and isoscalar giant dipole resonance (21.3 MeV, 90% energy-weighted sum-rule strength).