By solving the two-electron time-dependent Schrödinger equation, we study carrier-envelope-phase (CEP) effects on ionization plus excitation of He to He${}^{+}(n=2)$ states by a few-cycle attosecond pulse with a carrier frequency of 51 eV. For most CEPs the asymmetries in the photoelectron angular distributions with excitation of He${}^{+}\left(2s\right)$ or He${}^{+}\left(2p\right)$ have opposite signs and are two orders of magnitude larger than for ionization without excitation. These results indicate that attosecond pulse CEP effects may be significantly amplified in correlated two-electron ionization processes.

• Received 26 October 2012

DOI:https://doi.org/10.1103/PhysRevA.88.011401