Author:
Wang Siyang,Yan Jieyu,de las Heras Alba,Song Sirius,Prodanov Aleksandar,Wu Zhihan,Hernández-García Carlos,Plaja Luis,Popmintchev Dimitar,Popmintchev Tenio
Abstract
We observe experimentally a secondary plateau in UV-driven high harmonic generation in the soft X-ray region, extending up to 300 eV, due to a simultaneous double-recombination of highly-correlated electrons in helium atoms.