Attosecond Dynamics in Molecules and Atoms: STIER


Streak Camera for Strong-Field Ionization

The attosecond streak camera measures the time dependence of  photoemission caused by an attosecond extreme ultra-violet pulse by deflecting photoelectrons with an optical laser field. The same principle holds when the optical field itself releases photoelectrons. However, the times at which strong-field ionization takes place are dictated by the field strength, which is coupled to the deflection caused by the field.

In the STIER (Subcycle Tracing of Ionization enabled by infra-Red) technique, we decouple ionization and deflection by using a few-cycle visible field for ionization and a phase-stable mid-infrared field for deflection, as seen below. This combination of laser pulses represents a Streak Camera for Strong-field Ionization. As demonstrated in Ref. [1], STIER allows identifying the discrete ionization bursts in a few-cycle laser pulse, providing insight into sub-cycle ionization dynamics.

The project ATTOCHEM aims at exploiting the STIER experiment for studying ultrafast chemical dynamics. The two laser fields can couple to molecular degrees of freedom which permits manipulating the course of photochemical reactions. Furthermore, STIER can be combined with the laser-STM technique to image the valence electron density in atoms and molecules in real time.

Figure 1 (a) Experimental setup for STIER experiments. The carrier-envelope phase (CEP) of the visible pulses are recorded in a Stereo-ATI CEP meter. After recombination on a silicon mirror, the beams are used in an experiment such as COLTRIMS. (b) Measured streaking trace for strong-field ionization of neon. The solid and dotted lines show the relative ionization yields measured for cosine-like few-cycle pulses point up or down, respectively.



This project has received funding from the EU’s Horizon2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement No. 657544.

Further reading
[1] M. Kübel, et al. Streak camera for strong-field ionization. Phys. Rev. Lett. 119, 183201 (2017).

Attosecond Science at uOttawa and NRC