M.A. Van Hove, LBNL and U. of California, Davis
Very few theorists perform "theory of the experiment", compared to "predictive theory". The interpretation of diffraction experiments is a prime example: a handful of theorists develop x-ray absorption fine structure, photoelectron diffraction and holography, etc.
Our group [1] has recently focused on different forms of photoelectron diffraction (PD), primarily linked to experiments performed at the Advanced Light Source. A computer program (MSCD) [2], has been developed based on a cluster model and the Rehr-Albers separable representation. With "simple" PD, both in energy-scanned and angle-scanned modes, surface structures have been analyzed [1]. We have also explored circular dichroism in angular distributions (CDAD) [3] in preparation for work on magnetic circular dichroism (MCD) [4] to study magnetic surfaces. We are currently extending our codes to include both relativistic and magnetic effects.
We have applied a variety of holographic methods to photoelectron diffraction data [5]. In particular, we have explored the possibility of imaging magnetic structure through spin-polarized photoelectron holography [6].
We are also studying theoretically the new technique of multi-atom resonance photoemission (MARP), invented by Fadley [7]; it should permit determining the chemical identity of near neighbors to emitter atoms.
In the near future, we wish to develop valence photoemission, in order to enable the study of valence band structure and valence molecular orbitals, in collaboration with the group of Prof. W. Schattke of the University of Kiel in Germany [8].
At LBNL, we propose to create a "seamless computing environment". It will integrate experiment, computation and theory to enhance user-friendliness and reduce the time from measurement to publication. This will include a "collaboratory" mode, allowing remote collaborations over the Internet with a common project repository ("electronic notebook").
Such a collaboratory scheme will ease the formation of a "virtual" Photon Spectroscopy Theory Center funded by US-DOE. I also urge an international approach, especially in "theory of the experiment", to capitalize on efforts done at and for all synchrotron facilities. The UK-focused Daresbury model will be very useful (Collaborative Computational Projects).
References:
[1] http://electron.lbl.gov/
[2] Y. Chen, F.J. García de Abajo, A. Chassé, R.X. Ynzunza, A.P. Kaduwela, M.A. Van Hove and C.S. Fadley, subm. to Phys. Rev. B; http://electron.lbl.gov/mscdpack/mscdpack.html
[3] C. Westphal, A.P. Kaduwela, C.S. Fadley and M.A. Van Hove, Phys. Rev. B50, 6203-8 (1994); A.P. Kaduwela, H. Xiao, S. Thevuthasan, C.S. Fadley and M.A. Van Hove, Phys. Rev. B52, 14927-34 (1995); K. Starke, A.P. Kaduwela, Y. Liu, P.D. Johnson, M.A. Van Hove, C.S. Fadley, V. Chakarian, E.E. Chaban, G. Meigs and C.T. Chen, Phys. Rev. B53, 10544-7 (1996)
[4] M.A. Van Hove, A.P. Kaduwela, H. Xiao, W. Schattke and C.S. Fadley, J. El. Spectr. Rel. Phen. 80, 137-42 (1996); A. Fanelsa, R. Schellenberg, F.U. Hillebrecht, E. Kisker, J.G. Menchero, A.P. Kaduwela, C.S. Fadley and M.A. Van Hove, Phys. Rev. B54, 17962-5 (1996); R. Schellenberg, E. Kisker, A. Fanelsa, F.U. Hillebrecht, J.G. Menchero, A.P. Kaduwela, C.S. Fadley and M.A. Van Hove, Phys. Rev. B57, 14310-9 (1998).
[5] P.M. Len, J.D. Denlinger, E. Rotenberg, S. Kevan, B.P. Tonner, Y. Chen, M.A. Van Hove and C.S. Fadley, subm. to Phys. Rev. B.
[6] A.P. Kaduwela, Z. Wang, S. Thevuthasan, M.A. Van Hove and C.S. Fadley, Phys. Rev. B50, 9656-9 (1994).
[7] A. Kay, E. Arenholz, S. Mun, J. García de Abajo, C.S. Fadley, R. Denecke, Z. Hussain and M.A. Van Hove, to appear in Science (1998).
[8] C. Solterbeck, W. Schattke, J.-W. Zahlmann-Nowitzki, K.-U. Gawlick, L. Kipp, M. Skibowski, C.S. Fadley and M.A. Van Hove, Phys. Rev. Lett. 79, 4681-4 (1997); http://www.tp.cau.de/schattke/