Energy Transfer Mechanism in Pr-Doped SrF$_{2}$ Crystals
Results of investigation of energy transfer mechanism in SrF2 crystals doped with Pr3+ ions are presented. Temperature dependences of 5d-4f and exciton emission in this material under X-ray excitation, and thermostimulated luminescence (TSL) in temperature range 80-300 K are studied. It has been established that in SrF2-Pr3+ crystals the consecutive electron-hole capture mechanism of energy transfer takes place. Also we found that hole centers made a contribution to energy transfer from primary electrons and holes to Pr3+ ions.
Creation of trapped electrons and holes in alkaline-earth fluoride crystals doped by rare-earth ions
Defects in Ce3+- and Eu2+-doped alkaline-earth fluorides, created by vacuum ultraviolet (UV) photons at energies lower than at the bandgap, were investigated by various methods: thermostimulated luminescence, photostimulated luminescence and optical absorption. The CaF2:Eu2+ thermoluminescence curves in the range of 60-330 K due to various types of trapped holes were the same after vacuum UV illumination as after x-irradiation. Thermoluminescence curves of Ce3+-doped alkaline-earth fluorides created by vacuum UV illumination or x-irradiation were generally similar. However, Vk thermoluminescence peaks were absent in vacuum UV illuminated CaF2:Ce3+ and SrF2:Ce3+ crystals. This fact is obviously associated with the presence of charge-compensating fluorine interstitials in Ce3+-doped crystals. The creation of Ce2+ characteristic bands was observed in photostimulated luminescence spectra as well as in optical absorption spectra of vacuum UV illuminated or x-irradiated Ce3+-doped crystals. The suppression of hole thermoluminescence peaks in CaF2:Eu2+ crystals by blue light is due to the photoionization of Eu+ ions. The proposed mechanism for the creation of trapped hole and trapped-electron defects by vacuum UV illumination involves charge-transfer-type transitions, in which the electron transfers from the valence band to an impurity level lying in the bandgap. Comparison of all energies involved of transitions in the crystals investigated shows that the sum of all the transition energies is less than that of the bandgap by 1.5-3.5 eV. This energy difference can be considered to be the energy of lattice relaxation around the created Ce2+ or Eu+ ions.
Warm Hands in Cold Age – On the Need of a New World Order of Care
The world is aging as fertility and mortality are both decreasing. This article focuses on practical care work for the elderly. Such work is done primarily by women even though a larger portion than previously is paid rather than unpaid. All over the world, most elderly care work is organized within the family, most often unpaid. Men receive more care from partners than women, while women receive more care from female relatives. When care work is paid, the payment is generally low. A comparison between Germany, Spain, and Sweden demonstrates similar gender patterns, even though the role of the state in supporting care differs considerably as do care workers' conditions. The sustainability of today's distribution and organization of care work is questioned as the need for care increases, and the possibility of more equal sharing of care work between women and men is explored.