Infrared and visible laser spectroscopy for highly-charged Ni-like ions

Abstract

Application of visible or infrared (IR) lasers for spectroscopy of highlycharged ions (HCI) has not been particularly extensive so far due to a mismatch in typical energies. We show here that the energy difference between the two lowest levels within the first excited configuration 3d 9 4s in Ni-like ions of heavy elements from Z N =60 to Z N =92 is within the range of visible or near-IR lasers. The wavelengths of these transitions are calculated within the relativistic model potential formalism and compared with other theoretical and limited experimental data. Detailed collisional-radiative simulations of non-Maxwellian and thermal plasmas are performed showing that photopumping between these levels using relatively moderate lasers is sufficient to provide a two-order of magnitude increase of the pumped level population. This accordingly results in a similar rise of the x-ray line intensity thereby allowing control of x-ray emission with visible/IR lasers. Keywords: Ni-like ions, visible and infrared lasers, spectroscopyLaser spectroscopy [1] has become one of the most exciting and successful fields of research. Its ubiquitous applications extend from laser-induced breakdown spectroscopy (LIBS) to laser cooling of atoms and molecules to optical lattices, to name a few. In practically all applications it is the neutral or lowcharge atoms (or molecules) that are the subject of visible or infrared (IR) laser

Hyperfine-structure-resolved laser spectroscopy of many-electron highly charged ions

“…Therefore, the investigation of the (3d 9 5=2 4s) J=3 → (3d 9 3=2 4s) J=2 and (3d 9 5=2 4s) J=3 → (3d 9 5=2 4s) J=2 transitions with the present laser spectroscopy scheme is also possible. The laser spectroscopy of (3d 9 5=2 4s) J=3 → (3d 9 5=2 4s) J=2 transitions in Ni-like ions has already been proposed, and their transition wavelengths have been systematically investigated by theoretical calculations 48 . Here, we follow the systematic study to discuss the versatility of the present laser spectroscopy.…”

“…High-resolution spectroscopy of the transition between highly excited metastable states is achieved with the aid of excitation processes in the EBIT plasma. A similar experimental scheme was proposed for 3d 9 4s in Ni-like HCIs 48 ; however, this has not yet been demonstrated. It is worth emphasizing that we operate the EBIT with a low magnetic field condition to suppress the Zeeman splitting and employ the evaporative cooling technique for reduction of the Doppler line broadening, leading to clear observation of the hyperfine splitting.…”

High resolution X-ray spectra of the time evolution of emission from metastable electronic states of highly charged Ni-like ions

“…3 . The separation of the E2 and E3 lines are smaller than our current experimental x-ray energy resolution, therefore the E2/M3 blend includes both the long-lifetime M3 and the about six orders of magnitude faster E2 transitions [ 20 ]. Due to experimental considerations, the beam currents must decrease with lower accelerating potential in order to mitigate sputtering caused by the decrease in electrostatic focusing provided by higher potentials.…”

“…By varying the electron beam energy and density, the effects on the charge state evolution and steady-state balance are studied. The population of the metastable state is highly sensitive to the electron beam density since, for increasing densities, impact excitation becomes the dominate depopulating process of the Ni-like 3d 4 s metastable level [ 20 ]. This allows for the tuning and fitting of these parameters in theoretical collisional radiative models and by extension, potentially determining relative values for the electron impact cross sections.…”

Hyperfine-structure-resolved laser spectroscopy of many-electron highly charged ions

“…High-resolution spectroscopy of the transition between highly excited metastable states is achieved with the aid of excitation processes in the EBIT plasma. A similar experimental scheme was proposed for 3d 9 4s in Ni-like HCIs [43]; however, this has not yet been demonstrated. It is worth emphasizing that we operate the EBIT with a low magnetic field condition to suppress the Zeeman splitting, and employ the evaporative cooling technique for reduction of the Doppler line broadening, leading to clear observation of the hyperfine-structures.…”