X-ray-assisted nuclear excitation by electron capture in optical laser-generated plasmas

Abstract

X-ray assisted nuclear excitation by electron capture (NEEC) into inner-shell atomic holes in a plasma environment generated by strong optical lasers is investigated theoretically. The considered scenario involves the interaction of a strong optical laser with a solid-state nuclear target leading to the generation of a plasma. In addition, intense x-ray radiation from an X-ray Free Electron Laser (XFEL) produces inner-shell holes in the plasma ions, into which NEEC may occur. As case study we consider the 4.85-keV transition starting from the 2.4 MeV long-lived 93m Mo isomer that can be used to release the energy stored in this metastable nuclear state. We find that the recombination into 2p 1/2 inner-shell holes is most efficient in driving the nuclear transition. Already at few hundred eV plasma temperature, the generation of inner-shell holes can allow optimal conditions for NEEC, otherwise reached for steady-state plasma conditions in thermodynamical equilibrium only at few keV. The combination of x-ray and optical lasers presents two advantages: first, NEEC rates can be maximized at plasma temperatures where the photoexcitation rate remains low. Second, with mJclass optical lasers and an XFEL repetition rate of 10 kHz, the NEEC excitation number can reach ∼ 1 depleted isomer per second and is competitive with scenarios recently envisaged at petawattclass lasers.

Nuclear Excitation by Muon Capture

“…Since both NEEC and NEµC depend on the interaction between nuclear and atomic environment, tight muon orbits are expected to provide higher nuclear excitation cross section than their electronic counter parts. In particular, here we report findings of NEµC integrated cross section up to 1.82 × 10 5 b eV, that is five orders of magnitude higher than any corresponding NEEC cross section reported so far [25][26][27][28][29].…”

Nuclear Excitation by Muon Capture

“…Since both NEEC and NEµC depend on the interaction between nuclear and atomic environment, tight muon orbits are expected to provide higher nuclear excitation cross section than their electronic counter parts. In particular, here we report findings of NEµC integrated cross section up to 1.82 × 10 5 b eV, that is five orders of magnitude higher than any corresponding NEEC cross section reported so far [25][26][27][28][29]. To evaluate the NEµC cross section we used the advanced theory based on the Feshbach projection operator formalism developed by A. Pálffy for the NEEC process and presented in Refs.…”

Superposition of nuclear states in multi-lambda systems using x-ray laser pulses

“…This is of special interest due to the existence of long-lived nuclear states or so-called nuclear isomers, which can store large quantities of energy over long periods of time [1]. Recently, due to the improvements in the x-ray free-electron laser (XFEL) [2][3][4][5][6][7], the interaction of nuclear systems with laser pulses has become much more important and has created a new branch in quantum optics called nuclear quantum optics [8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Bürvenich et al [22] have studied the interaction of XFEL with two-level nuclear systems theoretically, where, in their proposed method, the gap between the x-ray laser frequency and the nuclear transition frequency has been compensated by an accelerating nuclear beam.…”