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2. Cooling Dynamics of PhotoexcitedC6−andC6H−

Author

Ito, G., primary, Furukawa, T., additional, Tanuma, H., additional, Matsumoto, J., additional, Shiromaru, H., additional, Majima, T., additional, Goto, M., additional, Azuma, T., additional, and Hansen, K., additional

Published
2014
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4. Measurement of Helicity-Dependent Photoabsorption Cross Sections on the Neutron from 815 to 1825 MeV

Author

Dutz, H., primary, Helbing, K., additional, Krimmer, J., additional, Speckner, T., additional, Zeitler, G., additional, Ahrens, J., additional, Altieri, S., additional, Annand, J. R. M., additional, Anton, G., additional, Arends, H.-J., additional, Beck, R., additional, Bock, A., additional, Bradtke, C., additional, Braghieri, A., additional, v. Drachenfels, W., additional, Frommberger, F., additional, Godo, M., additional, Goertz, S., additional, Grabmayr, P., additional, Hasegawa, S., additional, Hansen, K., additional, Harmsen, J., additional, Heid, E., additional, Hillert, W., additional, Holvoet, H., additional, Horikawa, N., additional, Iwata, T., additional, Van Hoorebeke, L., additional, d’Hose, N., additional, Jennewein, P., additional, Kiel, B., additional, Klein, F., additional, Kondratiev, R., additional, Lang, M., additional, Lannoy, B., additional, Leukel, R., additional, Lisin, V., additional, Menze, D., additional, Meyer, W., additional, Michel, T., additional, Naumann, J., additional, Panzeri, A., additional, Pedroni, P., additional, Pinelli, T., additional, Preobrajenski, I., additional, Radtke, E., additional, Reicherz, G., additional, Rohlof, C., additional, Rostomyan, T., additional, Sauer, M., additional, Schoch, B., additional, Schumacher, M., additional, Tamas, G., additional, Thomas, A., additional, van de Vyver, R., additional, Weihofen, W., additional, and Zapadtka, F., additional

Published
2005
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7. First Measurement of the Gerasimov-Drell-Hearn Sum Rule forH1from 0.7 to 1.8 GeV at ELSA

Author

Dutz, H., primary, Helbing, K., additional, Krimmer, J., additional, Speckner, T., additional, Zeitler, G., additional, Ahrens, J., additional, Altieri, S., additional, Annand, J. R. M., additional, Anton, G., additional, Arends, H.-J., additional, Beck, R., additional, Bock, A., additional, Bradtke, C., additional, Braghieri, A., additional, v. Drachenfels, W., additional, Frommberger, F., additional, Godo, M., additional, Goertz, S., additional, Grabmayr, P., additional, Hasegawa, S., additional, Hansen, K., additional, Harmsen, J., additional, Heid, E., additional, Hillert, W., additional, Holvoet, H., additional, Horikawa, N., additional, Iwata, T., additional, Hoorebeke, L. Van, additional, d’Hose, N., additional, Jennewein, P., additional, Kiel, B., additional, Klein, F., additional, Kondratiev, R., additional, Lang, M., additional, Lannoy, B., additional, Leukel, R., additional, Lisin, V., additional, Menze, D., additional, Meyer, W., additional, Michel, T., additional, Naumann, J., additional, Panzeri, A., additional, Pedroni, P., additional, Pinelli, T., additional, Preobrajenski, I., additional, Radtke, E., additional, Reicherz, G., additional, Rohlof, C., additional, Rostomyan, T., additional, Sauer, M., additional, Schoch, B., additional, Schumacher, M., additional, Tamas, G., additional, Thomas, A., additional, van de Vyver, R., additional, Weihofen, W., additional, and Zapadtka, F., additional

Published
2003
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8. Compton Scattering from the Deuteron and Extracted Neutron Polarizabilities

Author

Lundin, M., primary, Adler, J.-O., additional, Boland, M., additional, Fissum, K., additional, Glebe, T., additional, Hansen, K., additional, Isaksson, L., additional, Kaltschmidt, O., additional, Karlsson, M., additional, Kossert, K., additional, Levchuk, M. I., additional, Lilja, P., additional, Lindner, B., additional, L’vov, A. I., additional, Nilsson, B., additional, Oner, D. E., additional, Poech, C., additional, Proff, S., additional, Sandell, A., additional, Schröder, B., additional, Schumacher, M., additional, and Sims, D. A., additional

Published
2003
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9. Dynamic Jahn-Teller Effects in Isolated C Studied by Near-Infrared Spectroscopy in a Storage Ring

Author

Tomita, S., Andersen, J. U., Bonderup, E., Hvelplund, P., Liu, B., Brøndsted, Nielsen S., Pedersen, U. V., Rangama, J., Hansen, K., and Echt, O.

Subjects
ComputingMethodologies_DOCUMENTANDTEXTPROCESSING
Abstract

application/pdf, We have measured the near-infrared absorption spectrum for isolated C ions at room temperature. Two bands, at 9145 cm-1 and 10460 cm-1, have been identified in addition to the main absorption band at 9382 cm-1, seen also at low temperature in a matrix. An interpretation based on the theory of dynamic Jahn-Teller effects is proposed.

Published
2005

11. Helicity AmplitudesA1/2andA3/2for theD13(1520)Resonance Obtained from theγ→p→→pπ0Reaction

Author

Ahrens, J., primary, Altieri, S., additional, Annand, J. R. M., additional, Anton, G., additional, Arends, H.-J., additional, Aulenbacher, K., additional, Beck, R., additional, Bradtke, C., additional, Braghieri, A., additional, Degrande, N., additional, d'Hose, N., additional, Drechsel, D., additional, Dutz, H., additional, Goertz, S., additional, Grabmayr, P., additional, Hansen, K., additional, Harmsen, J., additional, von Harrach, D., additional, Hasegawa, S., additional, Hasegawa, T., additional, Heid, E., additional, Helbing, K., additional, Holvoet, H., additional, Van Hoorebeke, L., additional, Horikawa, N., additional, Iwata, T., additional, Jahn, O., additional, Jennewein, P., additional, Kageya, T., additional, Kamalov, S., additional, Kiel, B., additional, Klein, F., additional, Kondratiev, R., additional, Kossert, K., additional, Krimmer, J., additional, Lang, M., additional, Lannoy, B., additional, Leukel, R., additional, Lisin, V., additional, Matsuda, T., additional, McGeorge, J. C., additional, Meier, A., additional, Menze, D., additional, Meyer, W., additional, Michel, T., additional, Naumann, J., additional, Panzeri, A., additional, Pedroni, P., additional, Pinelli, T., additional, Preobrajenski, I., additional, Radtke, E., additional, Reichert, E., additional, Reicherz, G., additional, Rohlof, Ch., additional, Rosner, G., additional, Ryckbosch, D., additional, Sauer, M., additional, Schoch, B., additional, Schumacher, M., additional, Seitz, B., additional, Speckner, T., additional, Takabayashi, N., additional, Tamas, G., additional, Thomas, A., additional, Tiator, L., additional, van Vyver, R., additional, Wakai, A., additional, Weihofen, W., additional, Wissmann, F., additional, Zapadtka, F., additional, and Zeitler, G., additional

Published
2002
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13. First Measurement of the Gerasimov-Drell-Hearn Integral forH1from 200 to 800 MeV

Author

Ahrens, J., primary, Altieri, S., additional, Annand, J. R. M., additional, Anton, G., additional, Arends, H.-J., additional, Aulenbacher, K., additional, Beck, R., additional, Bradtke, C., additional, Braghieri, A., additional, Degrande, N., additional, d'Hose, N., additional, Dutz, H., additional, Goertz, S., additional, Grabmayr, P., additional, Hansen, K., additional, Harmsen, J., additional, von Harrach, D., additional, Hasegawa, S., additional, Hasegawa, T., additional, Heid, E., additional, Helbing, K., additional, Holvoet, H., additional, Van Hoorebeke, L., additional, Horikawa, N., additional, Iwata, T., additional, Jennewein, P., additional, Kageya, T., additional, Kiel, B., additional, Klein, F., additional, Kondratiev, R., additional, Kossert, K., additional, Krimmer, J., additional, Lang, M., additional, Lannoy, B., additional, Leukel, R., additional, Lisin, V., additional, Matsuda, T., additional, McGeorge, J. C., additional, Meier, A., additional, Menze, D., additional, Meyer, W., additional, Michel, T., additional, Naumann, J., additional, Owens, R. O., additional, Panzeri, A., additional, Pedroni, P., additional, Pinelli, T., additional, Preobrajenski, I., additional, Radtke, E., additional, Reichert, E., additional, Reicherz, G., additional, Rohlof, Ch., additional, Ryckbosch, D., additional, Sadiq, F., additional, Sauer, M., additional, Schoch, B., additional, Schumacher, M., additional, Seitz, B., additional, Speckner, T., additional, Steigerwald, M., additional, Takabayashi, N., additional, Tamas, G., additional, Thomas, A., additional, van de Vyver, R., additional, Wakai, A., additional, Weihofen, W., additional, Wissmann, F., additional, Zapadtka, F., additional, and Zeitler, G., additional

Published
2001
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15. Helicity Dependence ofγp→Nπbelow 450 MeV and Contribution to the Gerasimov-Drell-Hearn Sum Rule

Author

Ahrens, J., primary, Altieri, S., additional, Annand, J. R. M., additional, Anton, G., additional, Arends, H.-J., additional, Aulenbacher, K., additional, Beck, R., additional, Bradtke, C., additional, Braghieri, A., additional, Degrande, N., additional, d'Hose, N., additional, Dutz, H., additional, Goertz, S., additional, Grabmayr, P., additional, Hansen, K., additional, Harmsen, J., additional, von Harrach, D., additional, Hasegawa, S., additional, Hasegawa, T., additional, Heid, E., additional, Helbing, K., additional, Holvoet, H., additional, Van Hoorebeke, L., additional, Horikawa, N., additional, Iwata, T., additional, Jennewein, P., additional, Kageya, T., additional, Kiel, B., additional, Klein, F., additional, Kondratiev, R., additional, Kossert, K., additional, Krimmer, J., additional, Lang, M., additional, Lannoy, B., additional, Leukel, R., additional, Lisin, V., additional, Matsuda, T., additional, McGeorge, J. C., additional, Meier, A., additional, Menze, D., additional, Meyer, W., additional, Michel, T., additional, Naumann, J., additional, Owens, R. O., additional, Panzeri, A., additional, Pedroni, P., additional, Pinelli, T., additional, Preobrajenski, I., additional, Radtke, E., additional, Reichert, E., additional, Reicherz, G., additional, Rohlof, Ch., additional, Ryckbosch, D., additional, Sadiq, F., additional, Sauer, M., additional, Schoch, B., additional, Schumacher, M., additional, Seitz, B., additional, Speckner, T., additional, Steigerwald, M., additional, Takabayashi, N., additional, Tamas, G., additional, Thomas, A., additional, van de Vyver, R., additional, Wakai, A., additional, Weihofen, W., additional, Wissmann, F., additional, Zapadtka, F., additional, and Zeitler, G., additional

Published
2000
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20. mTDependence of Boson Interferometry in Heavy Ion Collisions at the CERN SPS

Author

Beker, H., primary, Bøggild, H., additional, Boissevain, J., additional, Cherney, M., additional, Dodd, J., additional, Esumi, S., additional, Fabjan, C. W., additional, Fields, D. E., additional, Franz, A., additional, Hansen, K. H., additional, Holzer, E. B., additional, Humanic, T. J., additional, Jacak, B. V., additional, Jayanti, R., additional, Kalechofsky, H., additional, Kobayashi, T., additional, Kvatadze, R., additional, Lee, Y. Y., additional, Leltchouk, M., additional, Lörstad, B., additional, Maeda, N., additional, Medvedev, A., additional, Miake, Y., additional, Miyabayashi, A., additional, Murray, M., additional, Nagamiya, S., additional, Nishimura, S., additional, Noteboom, E., additional, Pandey, S. U., additional, Piuz, F., additional, Polychronakos, V., additional, Potekhin, M., additional, Poulard, G., additional, Sakaguchi, A., additional, Sarabura, M., additional, Shigaki, K., additional, Simon-Gillo, J., additional, Sondheim, W., additional, Sugitate, T., additional, Sullivan, J. P., additional, Sumi, Y., additional, van Hecke, H., additional, Willis, W. J., additional, Wolf, K., additional, and Xu, N., additional

Published
1995
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22. Search for Quark Deconfinement: Strangeness Production inpp,dd,pα, andααCollisions atsNN=31.5 and 44GeV

Author

Åkesson, T., primary, Albrow, M. G., additional, Almehed, S., additional, Benary, O., additional, Bøggild, H., additional, Botner, O., additional, Breuker, H., additional, Brody, H., additional, Burkert, V., additional, Callen, B., additional, Carter, A. A., additional, Carter, J. R., additional, Cecil, P., additional, Choi, Y., additional, Cleland, W. E., additional, Dam, P., additional, Dagan, S., additional, Dahl-Jensen, E., additional, Dahl-Jensen, I., additional, Damgaard, G., additional, Evans, W. M., additional, Fabjan, C. W., additional, Frandsen, P., additional, Frankel, S., additional, Frati, W., additional, Gordon, H., additional, Goerlach, U., additional, Hansen, K. H., additional, Hedberg, V., additional, Hooper, J. E., additional, Jarlskog, G., additional, Kessler, G., additional, Killian, T., additional, Kroeger, R., additional, Kulka, K., additional, Lans, J. v. d., additional, Lissauer, D., additional, Lörstad, B., additional, Ludlam, T., additional, McCubbin, N. A., additional, Møller, R., additional, Molzon, M., additional, Nielsen, B. S., additional, Olsen, L. H., additional, Oren, Y., additional, Rosso, E., additional, Rudge, A., additional, Specht, H., additional, Stumer, I., additional, Thompson, J. A., additional, Thorstensen, G., additional, Vella, E., additional, Williamson, J. W., additional, Willis, W. J., additional, Witzeling, W., additional, Woody, C., additional, and Zajc, W. A., additional

Published
1985
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23. Electron Scattering in the Excitation Region of the Delta Resonance on Nuclei withA=1 to 16

Author

O'Connell, J. S., primary, Dodge, W. R., additional, Lightbody, J. W., additional, Maruyama, X. K., additional, Adler, J. -O., additional, Hansen, K., additional, Schroder, B., additional, Bernstein, A. M., additional, Blomqvist, K. I., additional, Cottman, B. H., additional, Comuzzi, J. J., additional, Miskimen, R. A., additional, and Quinn, B. P., additional

Published
1984
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24. Measurement of Compton Scattering from the Deuteron and an Improved Extraction of the Neutron Electromagnetic Polarizabilities.

Author

Myers, L. S., Annand, J. R. M., Bradvik, J., Feldman, G., Fissum, K. G., Grieβhammer, H. W., Hansen, K., Henshaw, S. S., Isaksson, L., Jebali, R., Kovash, M. A., Lundin, M., McGovern, J. A., Middleton, D. G., Nathan, A. M., Phillips, D. R., Schröder, B., and Stave, S. C.

Subjects
*COMPTON scattering, *POLARIZABILITY (Electricity), *ELECTROMAGNETIC interactions, *ELECTRIC fields, *MAGNETIC fields, *PARTICLES (Nuclear physics), *PARTICLE interactions
Abstract

The electromagnetic polarizabilities of the nucleon are fundamental properties that describe its response to external electric and magnetic fields. They can be extracted from Compton-scattering data-and have been, with good accuracy, in the case of the proton. In contradistinction, information for the neutron requires the use of Compton scattering from nuclear targets. Here, we report a new measurement of elastic photon scattering from deuterium using quasimonoenergetic tagged photons at the MAX IV Laboratory in Lund, Sweden. These first new data in more than a decade effectively double the world data set. Their energy range overlaps with previous experiments and extends it by 20 MeV to higher energies. An analysis using chiral effective field theory with dynamical A(1232) degrees of freedom shows the data are consistent with and within the world data set. After demonstrating that the fit is consistent with the Baldin sum rule, extracting values for the isoscalar nucleon polarizabilities, and combining them with a recent result for the proton, we obtain the neutron polarizabilities as αn = [11.55+1.25(stat)+0.2(BSR)+ 0.8(th)] x 10-4 fm3 and βn = [3.65≠ 1.25(stat) +0.2(BSR) ≠ 0.8(th)] x 10-4 fm3, with X2 = 45.2 for 44 degrees of freedom. [ABSTRACT FROM AUTHOR]

Published
2014
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25. Cooling Dynamics of Photoexcited C6- and C6H-.

Author

Ito, G., Furukawa, T., Tanuma, H., Matsumoto, J., Shiromam, H., Majima, T., Goto, M., Azuma, T., and Hansen, K.

Subjects
*COOLING, *ANIONS, *VACUUM, *HYDROGEN atom, *EXCITED states
Abstract

We report conclusive evidence of an efficient cooling mechanism via the electronic radiative transitions of hot small molecular anions isolated in vacuum. We stored C6- and C6H- in an ion storage ring and observed laser-induced electron detachment with delays up to several milliseconds. The terminal hydrogen atom caused a drastic change in the decay profiles. The decay of photoexcited C6H- is slow and nonexponential, which can be explained by depletion cooling, whereas that for C6- occurs extremely fast, on a time scale below 0.1 ms and can only be explained by electronic radiative cooling via low-lying electronic excited states. [ABSTRACT FROM AUTHOR]

Published
2014
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26. Light-Induced Magnetization at the Nanoscale.

Author

Wätzel J, Rebernik Ribič P, Coreno M, Danailov MB, David C, Demidovich A, Di Fraia M, Giannessi L, Hansen K, Krušič Š, Manfredda M, Meyer M, Mihelič A, Mirian N, Plekan O, Ressel B, Rösner B, Simoncig A, Spampinati S, Stupar M, Žitnik M, Zangrando M, Callegari C, Berakdar J, and De Ninno G

Abstract

Triggering and switching magnetic moments is of key importance for applications ranging from spintronics to quantum information. A noninvasive ultrafast control at the nanoscale is, however, an open challenge. Here, we propose a novel laser-based scheme for generating atomic-scale charge current loops within femtoseconds. The associated orbital magnetic moments remain ferromagnetically aligned after the laser pulses have ceased and are localized within an area that is tunable via laser parameters and can be chosen to be well below the diffraction limit of the driving laser field. The scheme relies on tuning the phase, polarization, and intensities of two copropagating Gaussian and vortex laser pulses, allowing us to control the spatial extent, direction, and strength of the atomic-scale charge current loops induced in the irradiated sample upon photon absorption. In the experiment we used He atoms driven by an ultraviolet and infrared vortex-beam laser pulses to generate current-carrying Rydberg states and test for the generated magnetic moments via dichroic effects in photoemission. Ab initio quantum dynamic simulations and analysis confirm the proposed scenario and provide a quantitative estimate of the generated local moments.

Published
2022
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27. First Measurement of Coherent Elastic Neutrino-Nucleus Scattering on Argon.

Author

Akimov D, Albert JB, An P, Awe C, Barbeau PS, Becker B, Belov V, Bernardi I, Blackston MA, Blokland L, Bolozdynya A, Cabrera-Palmer B, Chen N, Chernyak D, Conley E, Cooper RL, Daughhetee J, Del Valle Coello M, Detwiler JA, Durand MR, Efremenko Y, Elliott SR, Fabris L, Febbraro M, Fox W, Galindo-Uribarri A, Gallo Rosso A, Green MP, Hansen KS, Heath MR, Hedges S, Hughes M, Johnson T, Kaemingk M, Kaufman LJ, Khromov A, Konovalov A, Kozlova E, Kumpan A, Li L, Librande JT, Link JM, Liu J, Mann K, Markoff DM, McGoldrick O, Moreno H, Mueller PE, Newby J, Parno DS, Penttila S, Pershey D, Radford D, Rapp R, Ray H, Raybern J, Razuvaeva O, Reyna D, Rich GC, Rudik D, Runge J, Salvat DJ, Scholberg K, Shakirov A, Simakov G, Sinev G, Snow WM, Sosnovtsev V, Suh B, Tayloe R, Tellez-Giron-Flores K, Thornton RT, Tolstukhin I, Vanderwerp J, Varner RL, Virtue CJ, Visser G, Wiseman C, Wongjirad T, Yang J, Yen YR, Yoo J, Yu CH, and Zettlemoyer J

Abstract

We report the first measurement of coherent elastic neutrino-nucleus scattering (CEvNS) on argon using a liquid argon detector at the Oak Ridge National Laboratory Spallation Neutron Source. Two independent analyses prefer CEvNS over the background-only null hypothesis with greater than 3σ significance. The measured cross section, averaged over the incident neutrino flux, is (2.2±0.7)×10^{-39}  cm^{2}-consistent with the standard model prediction. The neutron-number dependence of this result, together with that from our previous measurement on CsI, confirms the existence of the CEvNS process and provides improved constraints on nonstandard neutrino interactions.

Published
2021
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28. Single Photon Thermal Ionization of C_{60}.

Author

Hansen K, Richter R, Alagia M, Stranges S, Schio L, Salén P, Yatsyna V, Feifel R, and Zhaunerchyk V

Abstract

We report on experiments which show that C_{60} can ionize in an indirect, quasithermal boiloff process after absorption of a single photon. The process involves a large number of incoherently excited valence electrons and yields electron spectra with a Boltzmann distribution with temperatures exceeding 10^{4}  K. It is expected to be present for other molecules and clusters with a comparatively large number of valence electrons. The astrophysical consequences are briefly discussed.

Published
2017
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29. Detection of Recurrent Fluorescence Photons.

Author

Ebara Y, Furukawa T, Matsumoto J, Tanuma H, Azuma T, Shiromaru H, and Hansen K

Abstract

We have detected visible photons emitted from the thermally populated electronic excited state, namely recurrent fluorescence (RF), of C_{6}^{-} stored in an electrostatic ion storage ring. Clear evidence is provided to distinguish RF from normal fluorescence, based on the temporal profile of detected photons synchronized with the revolution of C_{6}^{-} in the ring, for which the time scale is far longer than the lifetime of the intact photoexcited state. The relaxation (cooling) process via RF is likely to be commonplace for isolated molecular systems and crucial to the stabilization of molecules in interstellar environments.

Published
2016
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30. Finding density functionals with machine learning.

Author

Snyder JC, Rupp M, Hansen K, Müller KR, and Burke K

Abstract

Machine learning is used to approximate density functionals. For the model problem of the kinetic energy of noninteracting fermions in 1D, mean absolute errors below 1 kcal/mol on test densities similar to the training set are reached with fewer than 100 training densities. A predictor identifies if a test density is within the interpolation region. Via principal component analysis, a projected functional derivative finds highly accurate self-consistent densities. The challenges for application of our method to real electronic structure problems are discussed.

Published
2012
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31. Structures, energetics, and dynamics of helium adsorbed on isolated fullerene ions.

Author

Leidlmair C, Wang Y, Bartl P, Schöbel H, Denifl S, Probst M, Alcamí M, Martín F, Zettergren H, Hansen K, Echt O, and Scheier P

Abstract

Helium adsorbed on C(60)(+) and C(70)(+) exhibits phenomena akin to helium on graphite. Mass spectra suggest that commensurate layers form when all carbon hexagons and pentagons are occupied by one He each, but that the solvation shell does not close until 60 He atoms are adsorbed on C(60)(+), or 62 on C(70)(+). Molecular dynamics simulations of C(60)He(n)(+) at 4 K show that the commensurate phase is solid. Helium added to C(60)He(32)(+) will displace some atoms from pentagonal sites, leading to coexistence of a registered layer of immobile atoms interlaced with a nonregistered layer of mobile atoms.

Published
2012
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32. Experimental check of the Gerasimov-Drell-Hearn sum rule for 1H.

Author

Dutz H, Helbing K, Krimmer J, Speckner T, Zeitler G, Ahrens J, Altieri S, Annand JR, Anton G, Arends HJ, Beck R, Bock A, Bradtke C, Braghieri A, v Drachenfels W, Frommberger F, Godo M, Goertz S, Grabmayr P, Hasegawa S, Hansen K, Harmsen J, Heid E, Hillert W, Holvoet H, Horikawa N, Iwata T, Hoorebeke LV, D'Hose N, Jennewein P, Kiel B, Klein F, Kondratiev R, Lang M, Lannoy B, Leukel R, Lisin V, Menze D, Meyer W, Michel T, Naumann J, Panzeri A, Pedroni P, Pinelli T, Preobrajenski I, Radtke E, Reicherz G, Rohlof C, Rostomyan T, Sauer M, Schoch B, Schumacher M, Tamas G, Thomas A, van de Vyver R, Weihofen W, and Zapadtka F

Abstract

For the first time we checked the fundamental Gerasimov-Drell-Hearn (GDH) sum rule for the proton experimentally in the photon energy range from 0.2-2.9 GeV with the tagged photon facilities at MAMI (Mainz) and ELSA (Bonn). New data of the doubly polarized total cross section difference are presented in the energy range from 1.6 to 2.9 GeV. The contribution to the GDH integral from 0.2-2.9 GeV yields [254+/-5(stat)+/-12(syst)] microb with negative contributions in the Regge regime at photon energies above 2.1 GeV. This trend supports the validity of the GDH sum rule.

Published
2004
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33. First Measurement of the Gerasimov-Drell-Hearn Sum Rule for 1H from 0.7 to 1.8 GeV at ELSA.

Author

Dutz H, Helbing K, Krimmer J, Speckner T, Zeitler G, Ahrens J, Altieri S, Annand JR, Anton G, Arends HJ, Beck R, Bock A, Bradtke C, Braghieri A, v Drachenfels W, Frommberger F, Godo M, Goertz S, Grabmayr P, Hasegawa S, Hansen K, Harmsen J, Heid E, Hillert W, Holvoet H, Horikawa N, Iwata T, Van Hoorebeke L, d'Hose N, Jennewein P, Kiel B, Klein F, Kondratiev R, Lang M, Lannoy B, Leukel R, Lisin V, Menze D, Meyer W, Michel T, Naumann J, Panzeri A, Pedroni P, Pinelli T, Preobrajenski I, Radtke E, Reicherz G, Rohlof C, Rostomyan T, Sauer M, Schoch B, Schumacher M, Tamas G, Thomas A, van de Vyver R, Weihofen W, and Zapadtka F

Abstract

To verify the fundamental Gerasimov-Drell-Hearn (GDH) sum rule for the first time experimentally, we measured the helicity dependent total photoabsorption cross section with circularly polarized real photons and longitudinally polarized nucleons in the photon energy range 0.68-1.82 GeV with the tagged photon facility at ELSA. The experiment was carried out with a 4pi detection system, a circularly polarized tagged photon beam, and a frozen spin polarized proton target. The contribution to the GDH sum rule in this photon energy range is [49.9+/-2.4(stat)+/-2.2(syst)] microb.

Published
2003
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34. Helicity amplitudes A1/2 and A3/2 for the D13(1520) resonance obtained from the gamma-->p-->-->ppi(0) Reaction.

Author

Ahrens J, Altieri S, Annand JR, Anton G, Arends HJ, Aulenbacher K, Beck R, Bradtke C, Braghieri A, Degrande N, D'Hose N, Drechsel D, Dutz H, Goertz S, Grabmayr P, Hansen K, Harmsen J, Von Harrach D, Hasegawa S, Hasegawa T, Heid E, Helbing K, Holvoet H, Van Hoorebeke L, Horikawa N, Iwata T, Jahn O, Jennewein P, Kageya T, Kamalov S, Kiel B, Klein F, Kondratiev R, Kossert K, Krimmer J, Lang M, Lannoy B, Leukel R, Lisin V, Matsuda T, McGeorge JC, Meier A, Menze D, Meyer W, Michel T, Naumann J, Panzeri A, Pedroni P, Pinelli T, Preobrajenski I, Radtke E, Reichert E, Reicherz G, Rohlof Ch, Rosner G, Ryckbosch D, Sauer M, Schoch B, Schumacher M, Seitz B, Speckner T, Takabayashi N, Tamas G, Thomas A, Tiator L, Van Vyver R, Wakai A, Weihofen W, Wissmann F, Zapadtka F, and Zeitler G

Abstract

The helicity dependence of the gamma-->p-->-->ppi(0) reaction has been measured for the first time in the photon-energy range from 550 to 790 MeV. The experiment, performed at the Mainz microtron MAMI, used a 4pi-detector system, a circularly polarized, tagged photon beam, and a longitudinally polarized frozen-spin target. These data are predominantly sensitive to the D13(1520) resonance and are used to determine its helicity amplitudes.

Published
2002
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35. Observation of a 1/t decay law for hot clusters and molecules in a storage ring.

Author

Hansen K, Andersen JU, Hvelplund P, Møller SP, Pedersen UV, and Petrunin VV

Abstract

The exponential law is valid both for decay from a single quantum state into a continuum and for an ensemble maintained in thermal equilibrium. For statistical decay of an ensemble of isolated systems with a broad energy distribution, the exponential decay is replaced by a 1/t distribution. We present confirmation of this decay law by experiments with cluster anions in a small electrostatic storage ring. Deviations from the 1/t law for such an ensemble give important information on the dynamics of the systems. As examples, we present measurements revealing strong radiative cooling of anions of both metal clusters and fullerenes.

Published
2001
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36. Helicity dependence of gammap --> Npi below 450 MeV and contribution to the Gerasimov-Drell-Hearn sum rule.

Author

Ahrens J, Altieri S, Annand JR, Anton G, Arends H, Aulenbacher K, Beck R, Bradtke C, Braghieri A, Degrande N, d'Hose N, Dutz H, Goertz S, Grabmayr P, Hansen K, Harmsen J, von Harrach D, Hasegawa S, Hasegawa T, Heid E, Helbing K, Holvoet H, Van Hoorebeke L, Horikawa N, Iwata T, Jennewein P, Kageya T, Kiel B, Klein F, Kondratiev R, Kossert K, Krimmer J, Lang M, Lannoy B, Leukel R, Lisin V, Matsuda T, McGeorge JC, Meier A, Menze D, Meyer W, Michel T, Naumann J, Owens RO, Panzeri A, Pedroni P, Pinelli T, Preobrajenski I, and Radtke E

Abstract

The helicity dependence of the single pion photoproduction on the proton has been measured in the energy range from 200 to 450 MeV for the first time. The experiment, performed at the Mainz microtron MAMI, used a 4pi-detector system, a circularly polarized, tagged photon beam, and a frozen-spin target. The data obtained provide new information for multipole analyses of pion photoproduction and determine the main contributions to the Gerasimov-Drell-Hearn sum rule and the forward spin polarizability gamma(0).

Published
2000
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37. From above threshold ionization to statistical electron emission: the laser pulse-duration dependence of C60 photoelectron spectra

Author

Campbell EE, Hansen K, Hoffmann K, Korn G, Tchaplyguine M, Wittmann M, and Hertel IV IV

Abstract

The photoelectron spectra of C60 ionized using a 790 nm laser with pulse durations varying from 25 fs to 5 ps have been determined. For 25 fs pulses, in the absence of fragmentation, the ionization mechanism is direct multiphoton ionization with clear observation of above threshold ionization. As the pulse duration is increased, this becomes dominated by a statistical ionization due to equilibration among the electronic degrees of freedom. For pulse durations on the order of a ps coupling to the vibrational degrees of freedom occurs and the well-known phenomenon of delayed (&mgr;s) ionization is observed.

Published
2000
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