Observation of channel phase lag in asymmetric photoelectron angular distributions in the vicinity of autoionizing resonances

We report the results of channel phase lag measurements in the photoionization of atomic barium. We ionize the 6s6p $^{1}$P$_{1}$ excited state via a coherent laser field consisting of two frequencies, $\omega $ and 2$\omega $, to excite the atom to an autoionizing resonance in the series converging on the 5d$_{5/2}$ threshold. We present the channel phase lag observed for the asymmetric angular distribution for different ionization product states at different locations of the autoionizing resonances.