6. March 2019

Marc Vrakking

Attosecond Science: Past, Present and Future

Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy / Berlin, Germany

The last decade has witnessed spectacular progress in the way that attosecond laser pulses generated by high-harmonic generation (HHG) are used to study time-resolved electron dynamics. Starting from an initial emphasis on the generation and characterization of attosecond laser pulses, the field of attosecond science has within the last few years witnessed a dramatic growth in the number of application areas where attosecond pump-probe spectroscopy is pursued, or where techniques that have been developed in the context of the emergence of attosecond science are used to great advantage. A particularly significant example of the latter is the widespread use of time-resolved core-level spectroscopy using large bandwidth extreme ultra-violet (XUV) and soft X-ray pulses, which is finding application in both gas phase and condensed phase experiments.

In my talk I will present an overview of these developments, using a number of experiments that were recently performed at the MBI as illustration. I will discuss, among other things, experiments where femtosecond and attosecond time-resolved core level spectroscopy is used to investigate photodissociation dynamics and field-driven electron dynamics in the CH3I molecule[1, 2], as well as experiments on magnetization dynamics in thin Co/Pt films[3] and experiments on the coupling of electronic and nuclear motion in ionic crystals[4]. Moreover, I will show how the time seems ripe for novel applications of time-resolved core level spectroscopy in the condensed phase that venture deeply into the water window[5].

At the same time, attosecond seems to be on the verge of significantly extending its arsenal of available techniques. Besides the emerging possibilities to generate attosecond pulses at free electron laser facilities, these opportunities include, on the laboratory-scale, the development of attosecond pump-probe spectroscopy at high repetition rate[6-8], permitting the use of coincidence techniques, the realization of attosecond pump-attosecond probe spectroscopy, using high-harmonic sources that are able to reach previously inaccessible intensities[9], as well as novel ways to tailor the spatio-temporal distribution of XUV light produced by HHG[10]. 

References

1. Drescher, L., et al., Communication: XUV transient absorption spectroscopy of iodomethane and iodobenzene photodissociation. The Journal of Chemical Physics, 2016. 145(1): p. 011101.
2. Drescher, L., et al., State-Resolved Probing of Attosecond Timescale Molecular Dipoles. Journal of Physical Chemistry Letters, 2019. 10(2): p. 265-269.
3. Willems, F., et al., Probing ultrafast spin dynamics with high-harmonic magnetic circular dichroism spectroscopy. Physical Review B, 2015. 92(22): p. 220405.
4. Weisshaupt, J., et al., Ultrafast modulation of electronic structure by coherent phonon excitations. Physical Review B, 2017. 95(8): p. 081101.
5. Kleine, C., et al., Soft X-ray Absorption Spectroscopy of Aqueous Solutions Using a Table-Top Femtosecond Soft X-ray Source. Journal of Physical Chemistry Letters, 2019. 10(1): p. 52-58.
6. Furch, F.J., et al., CEP-stable few-cycle pulses with more than 190 mu J of energy at 100 kHz from a noncollinear optical parametric amplifier. Optics Letters, 2017. 42(13): p. 2495-2498.
7. Lu, C.H., et al., Sub-4 fs laser pulses at high average power and high repetition rate from an all-solid-state setup. Optics Express, 2018. 26(7): p. 8941-8956.
8. Hoff, D., et al., Continuous every-single-shot carrier-envelope phase measurement and control at 100 kHz. Optics Letters, 2018. 43(16): p. 3850-3853.
9. Rupp, D., et al., Coherent diffractive imaging of single helium nanodroplets with a high harmonic generation source (vol 8, 2017). Nature Communications, 2018. 9: p. 493.
10. Drescher, L., et al., Extreme-ultraviolet refractive optics. Nature, 2018(564): p. 91.

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