Modulation of photoemission anysotropy in molecular attosecond pump-probe ionization

Extreme ultraviolet attosecond pulses (XUV) can excite molecules into a coherent superposition of states, either in the bound region of the spectrum or encompassing several photoelectron-photoion pairs [1,2]. Such coherent wavepackets require a correlated wave-function approach to accurately describe their evolution. Here we present results computed with ASTRA (AttoSecond TRAnsitions), a new close-coupling implementation of the multichannel molecular ionization based on high-order transition density matrices between correlated ionic states [3]. We study the time-dependent asymmetry in the photoelectron angular distributions of excited ethylene and pyrazine, in which a coherent superposition of ∏_g and ∏_u states has been induced by an attosecond-XUV pulse. The anysotropy dynamics in the photoemission angular distribution can be mapped to the molecular valence charge migration, offering an experimental mean to its study [4]. ASTRA has been validated by comparing partial photoionization cross sections and molecular-frame photoelectron angular distributions for the CO, H₂CO, ethylene and pyrazine molecules, finding excellent agreement with benchmarks available in the literature [5,6].