Femtosecond laser pulses are used to record a movie of how electrons move within an argon ion
Ion momentum distribution after single and double ionization of a Ne+-ion beam
Using elliptically polarized laser fields the measured ion momentum distribution after single ionization exhibits a characteristic shape providing direct and complete information on the ionizing field strength as well as the ionization time.
Subsequently, after double ionization the ion momentum distribution is a convolution of the momenta of two electrons. Corresponding to the different emission directions a four- peaks structure appears in the momentum spectra of the ions.
We developed a deconvolution method which can be used to reconstruct the electron momenta in order to retrieve the averaged ionization times of all charge states created in the laser focus after multiple ionization with up to four ionization steps.
PHYSICAL REVIEW A 91, 031401(R) (2015)
(left) few-cycle laser pulse with different values of the CEP. (right) Distribution of the CEP
In very short laser pulses consisting of only a few optical cycles, the position of the maxima of the carrier wave relative to the pulse envelope, becomes an important parameter for applications in attosecond science. Figure 1 (left) illustrates how the carrier-envelope phase f determines the shape of a few-cycle laser pulse. Our group has a long standing history of developing techniques for the measurement of f, utilizing strong-field ionization.
For example, we have collaborated with scientists from the Unviersity of Erlangen in order to measure the CEP distribution in the focus of an intense laser pulse. In this experiment, a nanoscale metal tip was used as a phase sensitive probe to map out the phase distribution throughout the laser focus.
Figure 1 (left) illustration of a few-cycle laser pulse with different values of the carrier-envelope-phase (CEP). (right) Distribution of the CEP, obtained from our measurements.
- Hoff, et al. Tracing the phase of focused broadband laser pulses. Nature Phys13, 947–951 (2017)
- Zhang, et al., "Single-shot, real-time carrier-envelope phase measurement and tagging based on stereographic above-threshold ionization at short-wave infrared wavelengths," Opt. Lett. 42(24), 5150–5153 (2017).
- Rathje, et al., "Review of attosecond resolved measurement and control via carrier–envelope phase tagging with above-threshold ionization," J. Phys. B 45(7), 074003 (2012).
Femtosecond laser pulses are used to record a movie of how electrons move within an argon ion
We have demonstrated that photoelectron spectroscopy can be used to record movies of how electrons move on the tiniest scales, i.e. inside a single atom or molecule.
In our experiment, a first femtosecond laser pulse realizes a prototypical electron motion in an argon ion. As the electrons move within the ion, it takes less than 12 femtoseconds (0.000000000000012 seconds) for them to change from a donut shape into a peanut shape. Using a second laser pulse, we have imaged the distribution of the electrons within the ion, and, more importantly, how this distribution changes with time. The images are recorded by an electron detector and processed in a computer to retrieve a movie of the electron motion within the argon ion.
For more information, see: https://chemistrycommunity.nature.com/users/210278-matthias-kubel/posts/44625-watching-electrons-move-inside-atoms-and-moleculesExterner Link
M. Kübel, et al., Nat. Commun. 10(1), 1042 (2019).
Matthias Kübel-Schwarz, Dr.
