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Two-photon (VUV + visible) resonance ionization spectroscopy of molecular hydrogen

Description: Two-photon transitions have been examined in molecular hydrogen using coherent vacuum ultraviolet (VUV) photons at a fixed wavelength of 118 nm and a tunable photon from a dye laser. Though the VUV intensity is very weak (/approximately/100 nJ per pulse) it was utilized very efficiently since most VUV photons in the ionoization region were absorbed. This is the first time that coherent VUV light has been employed with tunable visible light for the production of two-photon spectra and the measur… more
Date: April 1, 1988
Creator: McCann, M.P.; Chen, C.H. & Payne, M.G.
Partner: UNT Libraries Government Documents Department
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High-intensity photoionization of H sub 2

Description: A tunable, high-intensity picosecond dye laser system has been employed with electron energy analysis to investigate the dynamics of (3+1) resonance-enhanced multiphoton ionization of H{sub 2} via different vibrational levels of its B{sub 1}{Sigma}{sub u}{sup +} and C{sup 1}{Pi}{sub u} electronic states. We observe production of molecular ions in various vibrational levels, with a shift to increased population of lower vibrational states of H{sub 2}{sup +} consistent with the a.c. Stark shift o… more
Date: May 1, 1991
Creator: Allendorf, S.W. & Szoeke, A.
Partner: UNT Libraries Government Documents Department
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Velocity distribution of laser photoionized neutrals ejected from methanol-dosed aluminium(111) by electron-stimulated desorption

Description: Nonresonant multiphoton ionization at 193 nm wavelength was employed for efficient detection of electron-stimulated neutral desorption from Al(111) dosed with methanol to produce monolayer methoxide coverage. Velocity spectra were measured by the flight time from the crystal surface to the focal region of the laser beam with a pulsed primary electron beam of 3 keV and the sample at 300 K. Either the C{sup +} or HCO{sup +} photofragment indicated the same non-Boltzmann velocity spectrum for the … more
Date: January 1, 1989
Creator: Young, C. E.; Whitten, J. E.; Pellin, M. J.; Gruen, D. M.; Jones, P. L. (Argonne National Lab., IL (USA) & Ohio State Univ., Columbus, OH (USA). Dept. of Chemistry)
Partner: UNT Libraries Government Documents Department
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Stimulated vuv radiation from HD excited by a picosecond ArF laser

Description: Stimulated emission on E,F ..-->.. B, B ..-->.. X, and C ..-->.. X transitions of HD is observed following two-photon excitation in the E,F state with a picosecond ArF* laser. The efficiency of the strongest B ..-->.. X line is approx.1%. Electron collisions are found to play an important role for C ..-->.. X emissions. 12 refs., 1 fig.
Date: January 1, 1984
Creator: Luk, T.S.; Egger, H.; Mueller, W.; Pummer, H. & Rhodes, C.K.
Partner: UNT Libraries Government Documents Department
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Trace analysis of osmium and rhenium by resonance ionization mass spectrometry of sputtered atoms

Description: The quantitative trace analysis of Os and Re was investigated using the surface analysis by resonance ionization of sputtered atoms (SARISA) apparatus developed at Argonne National Laboratory. SARISA samples the large fraction of sputtered neutral atoms and utilizes multiphoton resonance ionization to suppress atomic and molecular interferences. Matrix effects are considerably reduced for high ionization occurs in the gas phase and is independent of the physical properties of the substrate. Syn… more
Date: January 1, 1989
Creator: Blum, J. D.; Pellin, M. J.; Calaway, W. F.; Young, C. E.; Gruen, D. M.; Hutcheon, I. D. et al.
Partner: UNT Libraries Government Documents Department
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Nonadiabatic geometric phases of multiphoton transitions in dissipative systems and spin-j systems

Description: We present new developments in nonadiabatic geometric phases along two lines for systems undergoing changes of quantum state in intense fields. We first present a geometric representation of the non-Hermitian Schrodinger equation and introduce the notion of a complex multiphoton Aharonov-Anandan (AA) phase associated with dissipative two-level systems driven by periodic fields. The concept is further extended to include field modulation effects. We then develop the AA phase for spin-j systems i… more
Date: January 1, 1990
Creator: Layton, E.G. & Chu, Shih-I.
Partner: UNT Libraries Government Documents Department
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Multiphoton processes in scattering and ionization in an intense linearly-polarized radiation field

Description: We have employed the Gavrila-Kaminski formulation for the conversion of the time-dependent Schrodinger equation to a set of coupled differential equations that describe the interaction of an electron with a proton in the presence of an intense linearly-polarized radiation field in the Kramers-Henneberger gauge. The differential equations are solved numerically by a linear algebraic prescription effectively applied to electron-molecule collisions. We studied both electron-proton collisions assis… more
Date: January 1, 1992
Creator: Collins, L.A. (Los Alamos National Lab., NM (United States)) & Csanak, G. (Tsukuba Univ., Ibaraki (Japan))
Partner: UNT Libraries Government Documents Department
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Resonantly enhanced vacuum-ultraviolet generation and multiphoton ionization in carbon monoxide gas

Description: Competition between three-photon resonantly enhanced vacuum ultraviolet third-harmonic generation and six-photon multiphoton ionization using the A state in gaseous carbon monoxide is observed. Excitation spectra of the third-harmonic emission exhibit increasing blue shifts and broadening with increasing pressure due to the phase matching requirements. Estimates for the efficiency and tunability show that third-harmonic generation in carbon monoxide molecules is a promising source for coherent … more
Date: January 1, 1982
Creator: Glownia, J. H. & Sander, R. K.
Partner: UNT Libraries Government Documents Department
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Numerical simulations of multiphoton processes in many electron atoms

Description: In this report, we will present some details of two numerical methods which we have been pursuing for treating the multi-electron case. Both involve a numerical representation of the time dependent Hartree Fock electronic orbitals and a direct time integration of the coupled equations. Using these methods we will be able to determine the dynamics of the energy absorption process (preionization dynamics and the mechanism of ionization, i.e. whether it is direct multi-electron emission or sequent… more
Date: September 1, 1987
Creator: Kulander, K.C. & Cerjan, C.
Partner: UNT Libraries Government Documents Department
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Particle production through two-photon processes in relativistic heavy-ion colliders

Description: Particle production via two-photon processes in relativistic heavy-ion colliders is discussed. We consider the coherent production, including its impact parameter dependence, and incoherent production. Particular attention is given to Higgs boson production in the energy regime of the LHC and the SSC. 15 refs., 7 figs., 1 tab.
Date: January 1, 1991
Creator: Wu, J.-S.; Bottcher, C.; Strayer, M.R. (Oak Ridge National Lab., TN (United States)) & Shakin, C.M. (Brooklyn Coll., NY (United States))
Partner: UNT Libraries Government Documents Department
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Laser spectroscopy of sputtered atoms

Description: The use of laser radiation to study the sputtering process is of relatively recent origin. Much has been learned from this work about the basic physics of the sputtering process itself through measurements of velocity and excited state distributions of sputtered atoms and the effects of adsorbates on substrate sputtering yields. Furthermore, the identification, characterization, and sensitive detection of sputtered atoms by laser spectroscopy has led to the development of in situ diagnostics fo… more
Date: January 1, 1985
Creator: Gruen, D. M.; Pellin, M. J.; Young, C. E. & Calaway, W. F.
Partner: UNT Libraries Government Documents Department
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A multiphoton ionization technique for the determination of the ionization threshold of molecules in fluid media

Description: A new laser-induced multiphoton conductivity technique for the determination of the ionization threshold of molecules in fluids (liquids and dense gases) is described. Results are presented and discussed on aromatic molecules in nonpolar fluids. 2 refs., 1 fig., 1 tab.
Date: January 1, 1987
Creator: Faidas, H. & Christophorou, L.G.
Partner: UNT Libraries Government Documents Department
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Beamstrahlung spectra in next generation linear colliders

Description: For the next generation of linear colliders, the energy loss due to beamstrahlung during the collision of the e{sup +}e{sup {minus}} beams is expected to substantially influence the effective center-of-mass energy distribution of the colliding particles. In this paper, we first derive analytical formulae for the electron and photon energy spectra under multiple beamstrahlung processes, and for the e{sup +}e{sup {minus}} and {gamma}{gamma} differential luminosities. We then apply our formulation… more
Date: April 1, 1992
Creator: Barklow, T.; Chen, P. (Stanford Linear Accelerator Center, Menlo Park, CA (United States)) & Kozanecki, W. (DAPNIA-SPP, CEN-Saclay (France))
Partner: UNT Libraries Government Documents Department
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Multiphoton ionization of NO-rare gas van der Waals species

Description: To date, most spectroscopic studies of electronic states of clusters involving small molecules and rare gas (RG) atoms have employed laser-induced fluorescence techniques. Consequently, such studies (e.g., Levy and co-workers on I/sub 2/-RG species have been limited to the lowest lying electronic states, which are usually velance in character. Furthermore, the identification of the cluster often must be inferred from spectral shifts, pressure dependence, etc. We have applied the technique of mu… more
Date: January 1, 1985
Creator: Miller, J. C.
Partner: UNT Libraries Government Documents Department
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Resonantly-enhanced, four-photon ionization of krypton at laser intensities exceeding 10/sup 13/ W/cm/sup 2/

Description: The yield of singly- and multiply- charged ions of krypton and xenon is presented as a function of laser intensity and frequency. The measurements were performed using the second harmonic output of a well-characterized, tunable picosecond dye laser in the range 285 to 310 nm at laser intensities from 1 x 10/sup 12/ to 10/sup 14/ W/cm/sup 2/. Enhancement of the Kr/sup +/ yield by two orders of magnitude by three-photon resonant, four-photon ionization is observed in the vicinity of the 4d'(5/2)/… more
Date: December 1, 1987
Creator: Perry, M.D.; Landen, O.L. & Campbell, E.M.
Partner: UNT Libraries Government Documents Department
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Absolute rate measurements of two-photon process of gases, liquids, and solids

Description: Due to rapid improvements in high-power laser performance, two-photon absorption processes have become a very useful tool for studying the molecular structures of various gases, liquids and solids. However, measurements of absolute two-photon absorption cross sections were more or less ignored previously because of their small size. In this work, we obtained not only the two-photon absorption spectra, but also measurements of their absolute cross sections for various gases, liquids, and solids.… more
Date: December 1, 1987
Creator: Chen, C.H.; McCann, M.P. & Payne, M.G.
Partner: UNT Libraries Government Documents Department
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Beamstrahlung spectra in next generation linear colliders

Description: For the next generation of linear colliders, the energy loss due to beamstrahlung during the collision of the e{sup +}e{sup {minus}} beams is expected to substantially influence the effective center-of-mass energy distributions of the colliding particles. In this paper, we first derive analytical formulae for the electron and photon energy spectra under multiple beamstrahlung processes, and for the e{sup +}e{sup {minus}} and {gamma}{gamma} differential luminosities. We then apply our formalism … more
Date: February 1, 1992
Creator: Barklow, T.; Chen, P. (Stanford Linear Accelerator Center, Menlo Park, CA (United States)) & Kozanecki, W. (CEA Centre d'Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France))
Partner: UNT Libraries Government Documents Department
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Detection of single atoms by resonance ionization spectroscopy

Description: Rutherford's idea for counting individual atoms can, in principle, be implemented for nearly any type of atom, whether stable or radioactive, by using methods of resonance ionization. With the RIS technique, a laser is tuned to a wavelength which will promote a valence electron in a Z-selected atom to an excited level. Additional resonance or nonresonance photoabsorption steps are used to achieve nearly 100% ionization efficiencies. Hence, the RIS process can be saturated for the Z-selected ato… more
Date: January 1, 1986
Creator: Hurst, G.S.
Partner: UNT Libraries Government Documents Department
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Sixteenth International Conference on the physics of electronic and atomic collisions

Description: This report contains abstracts of papers on the following topics: photons, electron-atom collisions; electron-molecule collisions; electron-ion collisions; collisions involving exotic species; ion- atom collisions, ion-molecule or atom-molecule collisions; atom-atom collisions; ion-ion collisions; collisions involving rydberg atoms; field assisted collisions; collisions involving clusters and collisions involving condensed matter.
Date: January 1, 1989
Creator: Dalgarno, A.; Freund, R.S.; Lubell, M.S. & Lucatorto, T.B. (eds.)
Partner: UNT Libraries Government Documents Department
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Nuclear isomer separation

Description: We report experiments on selective photoionization of atoms containing isomeric nuclei of /sup 197/Hg. Other isomer separation techniques and their limitations are discussed.
Date: January 1, 1985
Creator: Dyer, P.
Partner: UNT Libraries Government Documents Department
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Precision spectroscopic measurements in few-electron ions

Description: We describe recent precision experiments in few-electron ions including measurements of the lifetimes of two-photon-emitting levels in Ni{sup 26+} and Ni{sup 27+}, a measurement of the lifetime of the 2{sup 3}S{sub 1} level in Br{sup 33+} and measurements of the 2{sup 3}S{sub 1} {yields} 2{sup 3}{sub 0,1,2} transition energies in B{sup 3+}. 13 refs., 4 figs.
Date: January 1, 1990
Creator: Dunford, R. W.; Berry, H. G.; Church, D. A.; Dinneen, T. P.; Hass, M.; Liu, C. J. et al.
Partner: UNT Libraries Government Documents Department
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Influence of internally generated fields on odd-photon pumping of dipole-allowed transitions in atomic gases

Description: The dramatic influence of multiwave mixing processes on resonant multiphoton excitation of dipole-allowed quantum transitions are discussed. Brief comparisons are made between different theoretical approaches used in treating the same underlying physics, and between the predictions and available experimental manifestations of the phenomenon for three-photon and five-photon induced processes.
Date: July 1, 1987
Creator: Garrett, W. R.
Partner: UNT Libraries Government Documents Department
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IR laser excitation in molecules: Chaos and diffusive energy growth

Description: After a short review of a generic vibrational model of ir multiple-photon excitation, the model is generalized to include rotations. It is shown that the combination of chaotic dynamics and rotational averaging leads to fluence-dependent absorption which removes the sensitivity of the results to model-dependent parameters. The classical rotation-vibration dynamics observed in this model correlate very well with quantum intuition based on a molecule's P, Q, and R-branch structure and on the red-… more
Date: January 1, 1987
Creator: Ackerhalt, J. R. & Milonni, P. W.
Partner: UNT Libraries Government Documents Department
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