Erlangen 2018 – scientific programme
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A: Fachverband Atomphysik
A 1: Cold atoms I - Rydbergs (joint session A/Q)
A 1.6: Talk
Monday, March 5, 2018, 11:45–12:00, K 0.011
The impact of ionization laser polarization on spatio-temporal distribution of photoelectrons from Cs atoms in a MOT — •Olena Fedchenko1, Sergey Chernov1, Melissa Vielle-Grosjean2, Gerd Schönhense1, and Daniel Comparat2 — 1Institut für Physik, JGU Mainz, Germany — 2University Paris-Sud, Orsay, France
We present results of investigation of the properties of a monochromatic photoelectron source based on near threshold photoionization of cold Cs atoms in MOT by time-of-flight momentum microscopy [1]. A 3D-stack of experimental results was obtained under absence of magnetic field. For this purpose a scheme with switched trapping B-field was used in the DC-MOT: 5 ms to load the MOT and 4 ms for excitation (@1470 nm, 1 ms exposition). Measurements were done for different linear polarizations of the ionizing Ti-sapphire fs-laser. Study of near-threshold photoionization with different gradients of the extracting electric field showed that the difference between signals with s- and p-polarization of the ionization light was due to real dichroism and partly due to contribution of field ionization of Rydberg states. Variation of the bandwidth of the Ti-sapphire laser revealed that in case of broad bandwidth several photoionization paths took place simultaneously. Namely, excitation of Rydberg atoms had place in the combination with subsequent field ionization and photoionization from higher states. To study the energy and time spread of photoelectrons, an accelerator with homogeneous pulsed electric field is proposed.
[1] O. Fedchenko et al., Appl. Phys. Lett, 111, 021104 (2017).