Erlangen 2018 – scientific programme

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MO: Fachverband Molekülphysik

MO 10: Strong laser fields - I (joint session A/MO)

MO 10.5: Talk

Tuesday, March 6, 2018, 15:15–15:30, K 2.019

Isotopic shifts measured via strong-field laser-atom interaction — •Nicolas Camus, Sofia Botsi, Lutz Fechner, Jose Crespo López-Urrutia, Thomas Pfeifer, and Robert Moshammer — Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany

High-precision measurements of isotopic shifts in the energy levels of atoms can provide sensitive tests of our understanding of relativistic and QED effects [1]. We present a novel spectroscopic method to measure small isotopic shifts utilizing the coherent population of different states arising from strong-field ionization. We experimentally measure the isotope shift between ³⁶Ar, ³⁸Ar and ⁴⁰Ar for the 3s² 3p⁵ (²P_3/2 → ²P_1/2) transition in singly charged argon ions. We measure it by implementing a Ramsey-like scheme using two ultrashort (6 fs) laser pulses. The first laser pulse excites the system into a coherent superposition of the aforementioned states by removing an electron from the atomic p-shell of the neutral atom. This superposition leads to a spin-orbit wave packet (SOWP) oscillating with a period of T = 23.3 fs that lasts for long times (tens of ns). The second delayed pulse probes, after ∼170.000 cycles, the wavepacket dynamics of the system by further ionization, allowing for a precision determination of the spin-orbit frequency at the ΔE/E ∼10⁻⁷ level . The detection of the different argon isotopes is made by a time-of-flight spectrometer. [1]. I. I. Tupitsyn et al., PRA 68, 022511 (2003)