Nondipole effects in double photoionization of He at 450 eV excess energy

We calculate photoelectron angular distributions for double photoionization of He at an excess energy of 450 eV including nondipole effects~[1]. We employ our model-independent representations~[2] for the dipole and quadrupole transition amplitudes and use the convergent close-coupling (CCC) approach~ [3] to evaluate them\footnote{Use of the Compaq AlphaServer SC National Facility of the Australian Partnership for Advanced Computing is acknowledged.}. Our nondipole results for the triply-differential cross section are shown to have improved agreement (as compared to the dipole approximation results) with recent experiments using linearly polarized light~[4] for a number of kinematical configurations. [1] A.Y. Istomin et al., J. Phys. B {\bf 39}, L35 (2006). [2] A.Y. Istomin et al., Phys. Rev. Lett. {\bf 92}, 063002 (2004). [3] A.S. Kheifets and I. Bray, Phys. Rev. A {\bf 57}, 2590 (1998). [4] A. Knapp et al., J. Phys. B {\bf 38}, 615 (2005).