Attosecond bound state dynamics

The response of electrons in the excited states of atoms are studied by attosecond transient absorption and sub-cycle gated harmonic emission. Isolated attosecond pulses with low photon energies (12 to 40 eV) are used to probe sub-optical-cycle dynamics in laser-perturbed atomic and molecular targets, revealing dynamic wavepacket interferences and coupled electron-nuclear dynamics[1].We demonstrate a dramatic enhancement of the below-threshold harmonics in the vicinity of atomic resonances[2]. The dependence on the driving laser carrier-envelope phase suggests a nonperturbative mechanism. Phase matching promises scalability to microJoule pulse energies.

1. M. Chini, Xiaowei Wang, Yan Cheng, Yi Wu, Di Zhao, D. A. Telnov, S-I Chu, and Zenghu Chang, "Sub-cycle Oscillations in Virtual States Brought to Light," Scientific Reports 3,1105(2013).

2. Michael Chini, Xiaowei Wang, Yan Cheng, He Wang, Yi Wu, Eric Cunningham, Peng-Cheng Li, John Heslar, Dmitry A. Telnov, Shih-I Chu, and Zenghu Chang,
"Coherent Phase-Matched VUV Generation by Field-Controlled Bound States," Nature Photonics 8,437(2014).