Reversible electron spirals by chirped attopulses at zero time delay

Abstract

A class of linear, spiral phenomena is discovered in the photoelectron momentum distribution when studying photoionization of $S$-state atoms by a pair of linearly chirped, oppositely circularly polarized attosecond pulses eventually delayed in time by $\ensuremath{\tau}$. This controllable effect, dubbed. reversible electron spirals because of its energy-dependent sense of rotation, is identified and can be isolated in the absence of time delay for the case of opposite chirp rates. The astrophysical concept of spiral arm pitch angle is borrowed to gain a better insight into the energy dependence of the reversible spiral rotation, to determine the attochirp as well as the binding energy characteristic of an atomic target. Our results indicate potential applications in attochirpmetry and polarimetry.