The photoluminescence of intentionally vanadium-doped ZnSe crystals displays at low temperatures (T approximately=4 K) the emission of the V3+ (d2), V2+ (d3) and V+ (d4) ions with different no-phonon structures at 5440, 4740 and 3640 cm-1, respectively. The excitation spectra of the V3+ and V2+ luminescence bands are investigated separately and exhibit structures of the respective spin-allowed as well as spin-forbidden internal transitions, which are largely in accordance with those of ZnS:V. The corresponding energy levels are approximated in a computation following the Tanabe-Sugano scheme. Furthermore, charge transfer processes at the luminescent centres are manifest in excitation, stimulation and transmission spectra. The vanadium ion proves to be an amphoteric impurity. Commencing from V2+, the state with neutral effective charge, light-induced transitions of donor and acceptor type are disclosed: V2+ to or from V3++eCB- and V2+ to or from V++eVB+.

The ep → e π + n reaction was studied in the first and second nucleon resonance regions in the 0.25 GeV 2 < Q 2 < 0.65 GeV 2 range by use of the CLAS detector at Thomas Jefferson National Accelerator Facility. For the first time, to our knowledge, the absolute cross sections were measured, covering nearly the full angular range in the hadronic center-of-mass frame. We extracted the structure functions σ T L , σ T T , and the linear combination σ T + σ L by fitting the φ dependence of the measured cross sections and compared them with the MAID and Sato-Lee models.

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