Date: April 11, 2019 Time: 9:30-11:00 Room: RIBF 2F Large Conference Hall (RIBF棟2F大会議室) Abstract: Gravitational potential wells due to galaxies, clusters of those, and filaments connecting them across the intergalactic space contain most of the baryonic matter at high virial temperatures. Under such conditions, atoms are stripped or highly ionized: protons and highly charged ions (HCI) overwhelm neutral matter. In other astrophysical environments, HCI are also very abundant: They govern the radiative transfer in stellar cores, shine from stellar coronae and supernova remnants, and even survive at closest distances to the event horizon of black holes while still emitting valuable spectroscopic signatures of those harsh environments. For fundamental theory, HCI are very interesting. Relativistic, quantum electrodynamic, and nuclear size effects are enormously magnified, while their electronic structure becomes simpler. Systematic studies along isoelectronic sequences ease access to such fundamental effects in the laboratory. In recent proposals, the insensitivity of HCI to external perturbations and the existence of highly forbidden optical transitions in many isoelectronic sequences were found to make HCI ideal candidates for optical frequency metrology references in ultra-stable clocks. Some specific HCI have been put forward for improved investigations of the time variation of fundamental constants, and experiments are already underway. The talk will present a general introduction to HCI, experimental results [1,2,3] and recent developments [4]. [1] An unexpectedly low oscillator strength as the origin of the Fe XVII emission problem, S. Bernitt et al., Nature 492, 225 (2012) [2] X-ray resonant photoexcitation: Linewidths and energies of Kα transitions in highly charged Fe ions, J. K. Rudolph, et al., Phys. Rev. Lett. 111, 103002 (2013) [3] Coulomb crystallization of highly charged ions, L. Schmöger et al., Science 347, 1233 (2015) [4] Highly charged ions: Optical clocks and applications in fundamental physics, M. G. Kozlov et al., Reviews of Modern Physics 90, 045005 (2018)
玉川 徹