Attosecond electronic dynamics of core-excited states of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi mathvariant="normal">N</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi mathvariant="normal">O</mml:mi></mml:mrow></mml:math> in the soft x-ray region
Nariyuki Saito, Nicolas Douguet, Hiroki Sannohe, Nobuhisa Ishii, Teruto Kanai, Yi Wu, Andrew Chew, Seunghwoi Han, Barry I. Schneider, Jeppe Olsen, Luca Argenti, Zenghu Chang, Jiro Itatani
Abstract
We present a combined experimental and theoretical study of the transient absorption spectroscopy of ${\mathrm{N}}_{2}\mathrm{O}$ at the N $K$ edge (400 eV) by employing an attosecond soft x-ray pulse and an overlapping intense femtosecond infrared pulse. Our experiment demonstrates that tunnel ionization of the core-excited states of neutral ${\mathrm{N}}_{2}\mathrm{O}$ causes prominent half-cycle oscillations in the absorption signal. In addition, we observe the appearance of the ${\mathrm{N}}_{2}{\mathrm{O}}^{+}$ signal with increasing delay as a result of the tunneling ionization of ${\mathrm{N}}_{2}\mathrm{O}$, thereby allowing us to follow the tunneling process in real time. We have developed theoretical models that allow us to interpret and reproduce the main trends of the experimental data.