Photoemission time delays

Ionization dynamics is quantified with lifetimes, rates and delays. A lifetime is a concept that only makes sense for an ensemble of systems and that is defined in the simplest case with an exponential decay law. If the photon energy exceeds the ionization potential of an atom, single-photon ionization can occur. The most established methods to measure such ionisation delays are attosecond streaking and reconstruction of attosecond beating by the interference of two-photon transitions (RABBITT), which are both two-color pump-probe schemes employing XUV attosecond pulses and a femtosecond infrared (IR) probe pulse.

Using a coincidence detection technique, we extended these measurements to gas mixtures, which allowed us to time the relative photoemission delay between two different atomic species.

[376] M. Sabbar, S. Heuser, R. Boge, M. Lucchini, L. Gallmann, C. Cirelli, U. Keller
Download"Combining attosecond XUV pulses with coincidence spectroscopy" (PDF, 922 KB)
Review of Scientific Instrument, vol. 85, 103113, 2014

In our measurements, we do not observe quantitative agreement between the experimental data and the theoretical Wigner delay without taking into account the presence of resonances in argon. In addition we have also confirmed recently that this is valid not only in the case of the attosecond streaking technique, but also when delays are retrieved with the RABBITT method:

[398] M. Sabbar, S. Heuser, R. Boge, M. Lucchini, T. Carette, E. Lindroth, L. Gallmann, C. Cirelli, U. Keller
Download"Resonance effects in photoemission time delays" (PDF, 440 KB)
Phys. Rev. Lett., vol. 115, 133001, 2015

[415] L. Cattaneo, J. Vos, M. Lucchini, L. Gallmann, C. Cirelli, U. Keller
Download"Comparison of attosecond streaking and RABBITT" (PDF, 3.7 MB)
Optics Express, vol. 24, No. 25, pp. 29060-29076, 2016

[395] C. Cirelli, M. Sabbar, S. Heuser, R. Boge, M. Lucchini, L. Gallmann, U. Keller
Download"Energy dependent photoemission time delays of noble gas atoms using coincidence attosecond streaking" (PDF, 2.6 MB) – Invited Paper
IEEE J. Sel. Topics Quantum Electron., vol. 21 (5), 8700307, 2015

The RABBITT technique also allows for angular resolved measurements, which introduces, however, a measurement-induced angular dependence:

[416] S. Heuser, Á. Jiménez-Galán, C. Cirelli, C. Marante, M. Sabbar, R. Boge, M. Lucchini, L. Gallmann, I. Ivanov, A. S. Kheifets, J. M. Dahlström, E. Lindroth, L. Argenti, F. Martín and U. Keller
Download"Angular dependence of photoemission time delay in helium" (PDF, 3.6 MB)
Phys. Rev. A, vol. 94, 063409, 2016

[439] C. Cirelli, C. Marante, S. Heuser, C. L. M. Petersson, Á. J. Galán, L. Argenti, S. Zhong, D. Busto, M. Isinger, S. Nandi, S. Maclot, L. Rading, P. Johnsson, M. Gisselbrecht, M. Lucchini, L. Gallmann, J. M. Dahlström, E. Lindroth, A. L’Huillier, F. Martin, U. Keller
Download"Anisotropic photoemission time delays close to a Fano resonance" (PDF, 1.2 MB)
Nature Comm., vol. 9, 955, 2018