169 research outputs found
Coherent phonon and electron spectroscopy on surfaces using time-resolved second-harmonic generation
No full textRecommended from our members
STODIES OF SURFACES USING OPTICAL SECOND-HARMONIC GENERATION
Full text linkRecommended from our members
Studies of surfaces using optical second-harmonic generation
Full text linkThe experiments reported in this thesis demonstrate the use of second-harmonic generation (SHG) and sum-frequency generation (SFG) in reflection from surfaces to study various surface properties. The experiments firmly establish SHG as a viable new surface probe that complements existing surface probes in ultrahigh vacuum environments and is in many ways unique for studying interfaces between dense media. Surface structural symmetry can be revealed through the anisotropy in the SH signal from the surface as the sample is rotated about its normal. The form of this anisotropy is derived in theory and verified with an experiment on the Si(100) and (111) surfaces. The SHG and SFG signals from molecules adsorbed on noninteracting substrates have a direct relationship to the number, average orientation, and spectroscopic properties of the molecules. The SH intensity was used to measure the isotherm for adsorption of p-nitrobenzoic acid from ethanolic solution to fused silica. Experiments performed on a strongly-interacting well-characterized Rh(111) surface in ultrahigh vacuum establish the sensitivity of the SH probe in corroboration with other surface probes. For the first time, the SH coverage-dependence was fit by theory in a quantitative way for the case of O-atom adsorption. The sensitivity of SH to adsorption at different sites was established for CO on top- and bridge-sites. SHG was shown to be surface specific in that the SHG from alkali metal surfaces originates from the first two monolayers. SH sensitivity to the adsorption of catalytically-important hydrocarbons and to chemical processes such as benzene dehydrogenation was also demonstrated. 122 references, 27 figures, 2 tables
Electronic elections employing DES smartcards
No full textThis paper covers the design of a voting protocol which can be used to perform local electronic elections with the use of currently commercial available devices. In contradiction with other proposed voting schemes the new proposed protocol does not rely on properties of asymmetric cryptographic algorithms like RSA. If needed an asymetric protocol can be used to attain the needed functions in the new protocol. It uses some of the techniques proposed in [Rob98] to authenticate messages without the need of cryptographic keys on public systems. Design characteristics are anonymously, democratically, non-coercion and public verifiably. Meeting all of these requirements is probably impossible. In any proposed scheme implementing all but one of these requirements is achieved. A nice implementation feature of the designed system is that the needed technology is already available and widely spread implemented in electronic purse smartcards.Applied Science
Recommended from our members
Studies of Molecular Adsorbates at Interfaces by Optical Second-Armonic Generation
Full text linkOptical second-harmonic generation (SHG) is surface-specific and has the sensitivity to detect submonolayers of molecules. It can be applied to study molecular adsorbates at the interface between any two centrosymmetric media. This has been demonstrated by using dye and p-nitrobenzoic acid (PNBA) molecules adsorbed on smooth fused quartz substrates as examples. With resonant SHG, the S/sub 0/ A..-->.. S/sub 2/ transition of the adsorbed dye molecules was measured. From the polarization dependence of the SHG, the orientation of PNBA at both the air/quartz and the ethanol/quartz interfaces was deduced. By varying the concentration of PNBA in ethanol, an adsorption isotherm for PNBA at the ethanol/quartz interfaces was also obtained
Ultrafast Mid-infrared Pulse Generation
No full textWe discuss the applications of short mid-infrared pulses for time resolved spectroscopic measurements in several different areas. A review of the techniques used to generate mid-infrared pulses is presented. Recent results are described on mid-infrared pulse generation using a two color mode- locked Ti:sapphire laser. The infrared pulses are tuned from 7.5 to 12.5 μm and have duration of 500 fs.262525529Miranda, R.S., Tom, H.W.K., Johnson, A.M., Bridges, T.J., Aumiller, G.D., (1991) Opt. Lett., 16, p. 1859Miranda, R.S., Tom, H.W.K., Johnson, A.M., Bridges, T.J., Aumiller, G.D., (1992) Appl. Phys. Lett., 60, p. 1105Cavicchia, M.A., Alfano, R.R., (1994) Ultrafast Phenomena IX, p. 128. , paper MD29Elsaesser, T., Bauerle, R.J., Klann, R., Kaiser, W., (1990) Ultrafast Phenomena VII, p. 328Woerner, M., Frey, W., Portella, M.T., Ludwig, C., Elsaesser, T., Kaiser, W., (1994) Phys. Rev. B, 49, p. 17007Lohner, A., Woerner, M., Elsaesser, T., Kaiser, W., (1992) Ultrafast Phenomena VIII, p. 416Ludwig, C., Frey, W., Woerner, M., Elsaesser, T., (1993) Opt. Commun., 102, p. 447Nurmikko, A.V., Schwartz, B.D., (1982) J. Vac. Sci. Technol., 21, p. 229Sellmeier, A., Hühner, H.J., Abstreiter, G., Weimann, G., Schlapp, W., (1987) Phys. Rev. Lett., 59, p. 1345Bauerle, R.J., Elsaesser, T., Lobentanzer, H., Stolz, W., Ploog, K., (1989) Phys. Rev. B, 40, p. 10002West, L.C., Eglash, S.J., (1985) Appl. Phys. Lett., 46, p. 1156Park, J.S., Karunasiri, R.P.G., Wang, K.L., (1992) Appl. Phys. Lett., 61, p. 681Bethea, C.G., Levine, B.F., Hasnain, G., Walker, J., Malik, R.J., (1989) J. Appl. Phys., 66, p. 963De Barros, M.R.X., Becker, P.C., Miranda, R.S., West, L.C., Dunkel, J., Roberts, C.W., Stayt Jr., J.W., Swaminathan, V., (1994) Electron. Lett., 30, p. 1093Quack, M., (1989) Infrared Phys., 29, p. 441Shane, S.F., Rothberg, L., Dubois, L.H., Levinos, N.J., Morin, M., Harris, A.L., (1990) Ultrafast Phenomena VII, p. 362Jedju, T., Rothberg, L., Labrie, A., (1988) Opt. Lett., 13, p. 961Hochstrasser, R.M., Anfinrud, P.A., Diller, R., Han, C., Iannone, M., Lian, T., Locke, B., (1990) Ultrafast Phenomena VII, p. 429Lin, M., Jackson, T.A., Anfinrud, P.A., (1994) Ultrafast Phenomena IX, p. 597. , paper FB4Cesar, C.L., Islam, M.N., Soccolich, C.E., Feldman, R.D., Austin, R.F., German, K.R., (1990) Optics. Lett., 15, p. 1147Kean, P.N., Zhu, X., Crust, D.W., Grant, R.S., Langford, N., Sibbet, W., (1989) Opt. Lett., 14, p. 39Cesar, C.L., Islam, M.N., Soccolich, C.E., Feldman, R.D., Austin, R.F., German, K.R., (1990) Ultrafast Phenomena VII, p. 17Powers, P.E., Tang, C., Cheng, L.K., (1994) Opt.Lett., 19, p. 1439Crowell, R.A., Holtom, G.R., Xie, S.X., (1994) Ultrafast Phenomena IX, , Paper ThD23Corkum, P.B., (1983) Opt. Lett., 8, p. 514Rolland, C., Corkum, P.B., (1986) J. Opt. Soc. Am., B3, p. 1625Elazzabi, A.Y., Meyer, J., Hughes, M.K.Y., Johnson, S.R., (1994) Opt. Lett., 19, p. 898Becker, P.C., Gershoni, D., (1990) Ultrafast Phenomena VII, p. 81. , Springer Verlag, BerlinJedju, T., Rothberg, L., (1988) Appl. Opt., 27, p. 615Elsaesser, T., Nuss, M.C., (1991) Opt. Lett., 16, p. 411Hamm, P., Lauterwasser, C., Zinth, W., (1993) Opt. Lett., 18, p. 1943Yodh, A.G., Tom, H.W.K., Aumiller, G.D., Miranda, R.S., (1991) J. Opt. Soc. of Am., B8, p. 1663Socha, U., Hussong, J., Urschel, R., Nebel, A., Beigang, R., (1994) Conference on Laser and Electro Optics'94, p. 378. , paper CThQ2Kafka, J.D., Watts, M.L., Pieterse, J.W., (1994) Conference on Laser and Electro-Optics, 8. , OSA Technical Digest, paper CWI6Kafka, J.D., Watts, M.L., Pieterse, J.W., (1994) Ultrafast Phenomena IX, , Paper TuD21Seilmeier, A., Worner, M., Hbner, H.-J., Kaiser, W., (1988) Appl. Phys. Lett., 53, p. 2468De Barros, M.R.X., Becker, P.C., (1993) Opt. Lett., 18, p. 631LeBlanc, C., Grillon, G., Chambaret, J.P., Migus, A., Antonetti, A., (1993) Opt. Lett., 18, p. 140Zhou, J., Huang, C.-P., Shi, C., Murnane, M.M., Kapteyn, H.C., (1994) Opt. Lett., 19, p. 12
Recommended from our members
DETERMINATION OF MOLECULAR ORIENTATION OF MONOLAYER ADSORBATES BY OPTICAL SECOND-HARMONIC GENERATION
Full text link
- …
