Search Results - (Author, Cooperation:H. Walther)
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1Latest Papers from Table of Contents or Articles in PressJ. Kirkby ; J. Curtius ; J. Almeida ; E. Dunne ; J. Duplissy ; S. Ehrhart ; A. Franchin ; S. Gagne ; L. Ickes ; A. Kurten ; A. Kupc ; A. Metzger ; F. Riccobono ; L. Rondo ; S. Schobesberger ; G. Tsagkogeorgas ; D. Wimmer ; A. Amorim ; F. Bianchi ; M. Breitenlechner ; A. David ; J. Dommen ; A. Downard ; M. Ehn ; R. C. Flagan ; S. Haider ; A. Hansel ; D. Hauser ; W. Jud ; H. Junninen ; F. Kreissl ; A. Kvashin ; A. Laaksonen ; K. Lehtipalo ; J. Lima ; E. R. Lovejoy ; V. Makhmutov ; S. Mathot ; J. Mikkila ; P. Minginette ; S. Mogo ; T. Nieminen ; A. Onnela ; P. Pereira ; T. Petaja ; R. Schnitzhofer ; J. H. Seinfeld ; M. Sipila ; Y. Stozhkov ; F. Stratmann ; A. Tome ; J. Vanhanen ; Y. Viisanen ; A. Vrtala ; P. E. Wagner ; H. Walther ; E. Weingartner ; H. Wex ; P. M. Winkler ; K. S. Carslaw ; D. R. Worsnop ; U. Baltensperger ; M. Kulmala
Nature Publishing Group (NPG)
Published 2011Staff ViewPublication Date: 2011-08-26Publisher: Nature Publishing Group (NPG)Print ISSN: 0028-0836Electronic ISSN: 1476-4687Topics: BiologyChemistry and PharmacologyMedicineNatural Sciences in GeneralPhysicsPublished by: -
2Articles: DFG German National LicensesStaff View
ISSN: 0009-286XKeywords: Chemistry ; Industrial ChemistrySource: Wiley InterScience Backfile Collection 1832-2000Topics: Chemistry and PharmacologyProcess Engineering, Biotechnology, Nutrition TechnologyNotes: Es wird der gegenwärtige Stand der Ferngasversorgung und deren Verbundwirtschaft mit der chemischen Industrie geschildert. Außerdem werden die Maßnahmen zur Erzeugung und Einsparung hochwertiger Brenngase sowie die Untergrundspeicherung behandelt. Wie weit für die Ferngasversorgung bei der Gasreinigung und Kompression kältetechnische Probleme von Bedeutung sind, lassen zahlreiche Beispiele erkennen.Additional Material: 16 Ill.Type of Medium: Electronic ResourceURL: -
3FIS Bildung LiteraturdatenbankStaff View
Type of Medium: articlePublication Date: 1999Keywords: Sekundarstufe II ; Sachinformation ; Quantenelektrodynamik ; Ein-Atom-Experiment ; Ionen-Käfig ; Laserspektroskopie ; Physikunterricht ; Quantenmechanik ; Quantenphysik ; Quantentheorie ; ResonatorIn: Praxis der Naturwissenschaften. Physik, Bd. 48 (1999) H. 8, S. 20-27, 0177-83740342-8729Language: German -
4Latest Papers from Table of Contents or Articles in PressW. Roseker; S. O. Hruszkewycz; F. Lehmkühler; M. Walther; H. Schulte-Schrepping; S. Lee; T. Osaka; L. Strüder; R. Hartmann; M. Sikorski; S. Song; A. Robert; P. H. Fuoss; M. Sutton; G. B. Stephenson; G. Grübel
Nature Publishing Group (NPG)
Published 2018Staff ViewPublication Date: 2018-04-28Publisher: Nature Publishing Group (NPG)Electronic ISSN: 2041-1723Topics: BiologyChemistry and PharmacologyNatural Sciences in GeneralPhysicsPublished by: -
5Articles: DFG German National LicensesWoelker, M. ; Bein, B. K. ; Pelzl, J. ; Walther, H. G.
[S.l.] : American Institute of Physics (AIP)
Published 1991Staff ViewISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: Two aspects of the photothermal beam deflection experiment, which are essential for a quantitative interpretation and for an improved performance of the experiment are studied here: The alignment of the probe laser beam with respect to the pump beam and to the solid surface under investigation and, second, the smoothing of experimental data by convolution filtering.Type of Medium: Electronic ResourceURL: -
6Articles: DFG German National LicensesFriedrich, K. ; Haupt, K. ; Seidel, U. ; Walther, H. G.
[S.l.] : American Institute of Physics (AIP)
Published 1992Staff ViewISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: Photothermal imaging can be described quantitatively by means of a point spread function (PSF), which represents the image of a buried thermal point defect. From this PSF conclusions can be drawn about amplitude and phase contrast, half-width, and resolution of photothermal imaging. The theoretical findings are stated by measurements from an appropriately designed model sample.Type of Medium: Electronic ResourceURL: -
7Articles: DFG German National LicensesMatsuo, Y. ; Vach, H. ; Chaˆtelet, M. ; Häger, J. ; Roth, C. ; Flytzanis, C. ; Walther, H.
College Park, Md. : American Institute of Physics (AIP)
Published 1990Staff ViewISSN: 1089-7690Source: AIP Digital ArchiveTopics: PhysicsChemistry and PharmacologyNotes: We report on the scattering of supersonic NO molecules from a diamond (111) surface. Using state selective laser techniques combined with mass selective quadrupole measurements, we observe two novel features in the molecule–surface interaction: first, a scattering behavior which is dependent on the direction of the incoming molecules; and second, surface residence times that are unusually long, but temperature independent. The former observation can be traced back to the topography of the unreconstructed diamond (111) surface, the latter one can be understood when a temporary function of a metastable surface–molecule complex is assumed.Type of Medium: Electronic ResourceURL: -
8Articles: DFG German National LicensesVach, H. ; Häger, J. ; Walther, H.
College Park, Md. : American Institute of Physics (AIP)
Published 1989Staff ViewISSN: 1089-7690Source: AIP Digital ArchiveTopics: PhysicsChemistry and PharmacologyNotes: The rotational, angular, and translational scattering behavior of NO molecules prepared in a single ro-vibrational state before their interaction with a cleaved graphite surface was determined (v=1→v=1 process). Moreover, the deactivation probability of the vibrational energy into the rotational and translational motion of the molecule could be evaluated (v=1→v=0 process). Finally, it was possible to investigate the scattering behavior of NO molecules that experienced vibrational excitation during their surface encounter (v=0→v=1 process).Type of Medium: Electronic ResourceURL: -
9Articles: DFG German National LicensesKetterle, W. ; Dodhy, A. ; Walther, H.
College Park, Md. : American Institute of Physics (AIP)
Published 1988Staff ViewISSN: 1089-7690Source: AIP Digital ArchiveTopics: PhysicsChemistry and PharmacologyNotes: Spectra of helium hydride were observed after neutralization of a mass-selected HeH+ beam. The molecules were produced in a fast beam, and so a special setup had to be used to avoid Doppler broadening and a careful calibration procedure had to be applied to determine the line positions and linewidths. In an earlier paper, we reported the first observation of a discrete spectrum of helium hydride, which was discovered by means of an emission band near 8000 A(ring). In this paper, a detailed analysis of this band for all four stable isotopic mixtures is given. For the deuterides several vibrational bands were observed, which allowed equilibrium molecular constants to be determined. These constants agree with the results of recent ab initio calculations. The similarity of these constants to those of HeH+ in the ground state confirms that the observed states are Rydberg states. Comparison of the molecular constants for different isotopic mixtures shows deviations from the Born–Oppenheimer approximation. Born–Oppenheimer breakdown parameters were derived. Both the upper and lower states show predissociation to the repulsive ground state of helium hydride. The line intensities give evidence of a dependence of the electronic transition moment on the interatomic distance.Type of Medium: Electronic ResourceURL: -
10Articles: DFG German National LicensesStaff View
ISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: By means of a photoacoustic gas-cell technique we estimated the thickness of varnish layers on base paper. Interpretation of the measurements was supported by a theoretical model which describes the packaging material as a multilayer stack with freely eligible thermal and optical properties. The variable moisture content could be taken into account using mixture formulas for the definition of thermal effusivity and thermal diffusivity at different percentages of water. Satisfying correspondence between photoacoustic phase slope measurements and calculations simulating water migration was able to be achieved. © 2001 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
11Articles: DFG German National LicensesStaff View
ISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: Surface roughness effects have a remarkable influence on photothermal measurements from steel samples and seriously distort hardness depth profiling. The thermal response of rough surfaces is described by an effective layer whose properties are defined by global roughness numbers like root- mean square roughness and peak-to-valley-roughness. Calculations of roughness effects as well as measurements from rough steel samples were performed and compared to each other. A good correspondence between the model and experiment was found which demonstrates the suitability of the effective layer model for a description of roughness. © 2001 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
12Articles: DFG German National LicensesRoth, C. ; Häger, J. ; Walther, H.
College Park, Md. : American Institute of Physics (AIP)
Published 1992Staff ViewISSN: 1089-7690Source: AIP Digital ArchiveTopics: PhysicsChemistry and PharmacologyNotes: The translational, rotational, and vibrational dependencies of NO molecules scattered from a diamond (110) surface have been investigated for a series of scattering geometries. The integral and state selected angular distributions of the scattered molecules have been measured. In the exit channel the velocities of molecules in selected states as well as the rotational population distributions in the two lowest vibrational states (ν=0,1) were analyzed for a variety of incoming energies (200 cm−1≤Ekin≤2600 cm−1), scattering angles, and surface temperatures. Molecules with a fast incoming velocity and a rotational energy of Erot≤1000 cm−1 after scattering (about 75% of all molecules) exhibit an elastic interaction with the surface (no energy exchange with the surface, Ekin+Erot=const). For molecules receiving higher rotational energy during the scattering process (Erot≥1000 cm−1) an increasing influence of the surface temperature on their final rotational and translational motion was found. For slow incoming molecules such a dependence is also observed but less pronounced. About 5×10−3 of the incoming molecules are vibrationally excited during their encounter with the surface, and exhibit, after the scattering, angular, and rotational population distributions which are similar to those of the molecules which remain in the vibrational ground state during the scattering process. Rotation of the (110) surface around its normal by 90° leads to identical scattering results: there is no detectable influence of the various surface topographies on the molecular scattering behavior within our present experimental accuracy.Type of Medium: Electronic ResourceURL: -
13Articles: DFG German National LicensesStaff View
ISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: We proposed an approach for the estimation of the depth profile of thermally inhomogeneous samples from combined laterally and frequency resolved photothermal measurements. The mathematical procedure of data inversion makes use of the quasianalytical solution of the forward problem. Introducing an appropriately chosen grid of depth coordinates the Hankel transform of the surface temperature can be expressed by a continuous fraction formula. This enables the usage of the effective conjugated gradient technique to retrieve the thermal depth profiles by minimization of the objective function. Making use of the a priori information about the inhomogeneous sample we chose an appropriate Tikhonov‘s stabilizer function and by this way remarkably improved the iteration procedure. The success of this method consisted both in a drastically reduced computation time and in a better approximation of the searched profiles. This was demonstrated by numerical simulations modeling the case of surface hardened steel. © 1999 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
14Articles: DFG German National LicensesFink, M. ; Häger, J. ; Glatzer, D. ; Walther, H.
[S.l.] : American Institute of Physics (AIP)
Published 1993Staff ViewISSN: 1089-7623Source: AIP Digital ArchiveTopics: PhysicsElectrical Engineering, Measurement and Control TechnologyNotes: A pulsed supersonic nozzle is presented which can be heated to 1300 K and cooled to 4 K. The whole system is composed of quartz to prevent the decomposition of the molecules at a high temperature. The nozzle has produced gas pulses at a rate of 10 Hz and pulse lengths of 5 ms. The performance of the system is demonstrated by the flight time and the rotational temperature of NO molecules as a function of the stagnation pressure and the nozzle temperature.Type of Medium: Electronic ResourceURL: -
15Articles: DFG German National LicensesStaff View
ISSN: 1089-7623Source: AIP Digital ArchiveTopics: PhysicsElectrical Engineering, Measurement and Control TechnologyNotes: Photothermal radiometric (PTR) measurements from paint coated samples are compared with calculations taking into account the real ir spectrum of the coating. The photothermal signal phase was found to depend sensitively on the detected wavelength range. This fact has to be taken into consideration for the interpretation of PTR measurements. © 1996 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
16Articles: DFG German National LicensesStaff View
ISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: Surface problems in photothermal depth profiling of technical surfaces arise from the intrinsic optical absorptivity; therefore, it is not appropriate to use amplitude values for profile reconstruction. We report a reconstruction technique based only on phase data. The performance of this approach was tested successfully by measuring the thermal conductivity profiles of laser hardened steel samples. © 1996 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
17Articles: DFG German National LicensesSeidel, U. ; Haupt, K. ; Walther, H. G. ; Burt, J. A. ; Munidasa, M.
[S.l.] : American Institute of Physics (AIP)
Published 1995Staff ViewISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: Based on the description of photothermal image formation as a convolution between a defect distribution and the photothermal point spread function, a technique is presented by which subsurface thermal inhomogeneities can be quantitatively reconstructed from photothermal images. Numerical simulations demonstrate the performance and the limits of the suggested approach. Experimental results obtained from a low thermal contrast sample are presented and compared with the theory. © 1995 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
18Articles: DFG German National LicensesSeidel, U. ; Haupt, K. ; Walther, H. G. ; Burt, J. ; Bein, B. K.
[S.l.] : American Institute of Physics (AIP)
Published 1994Staff ViewISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: Calculated photothermal contrast functions arising from lateral scanning of buried stripe- and disk-shaped deviations in thermal conductivity k are presented. From the theoretical findings the measuring conditions are derived in terms of the modulation frequency for which optimal photothermal discrimination of subsurface thermal inhomogeneities can be achieved. The theoretical results have been verified experimentally be measuring model samples, in which localized inhomogeneities were embedded.Type of Medium: Electronic ResourceURL: -
19Articles: DFG German National LicensesSammet, C. ; Völcker, M. ; Krieger, W. ; Walther, H.
[S.l.] : American Institute of Physics (AIP)
Published 1995Staff ViewISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: Two infrared laser beams coupled into the tunneling junction of a scanning tunneling microscope lead to the generation of a signal at the difference frequency. In this article it is described that two different frequency mixing mechanisms are responsible for this process. One part of the signal is generated through a mixing process owing to the nonlinearity in the static current-voltage characteristic. Another part has its origin in a nonlinear susceptibility at the surface; it therefore corresponds to frequency mixing in nonlinear optics. It will be shown that the difference-frequency signals generated by the two processes can be separated owing to their different dependence on the tip-sample distance. © 1995 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
20Articles: DFG German National LicensesLan, T. T. N. ; Seidel, U. ; Walther, H. G.
[S.l.] : American Institute of Physics (AIP)
Published 1995Staff ViewISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: An analytical solution for the photothermally measurable surface temperature of a sample with piecewise linearly inhomogeneous depth profile of the thermal conductivity k is presented. Based on this solution an inversion algorithm using a sequence of one-parameter fits is suggested in order to estimate the k profile. Numerical simulations demonstrate the performance of the approach and its insensitivity to random errors. © 1995 American Institute of Physics.Type of Medium: Electronic ResourceURL: