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).