Valence-band electronic structure of YbXCu4 (X = In, Cd, Mg)
has been investigated by means of high-energy-resolution
photoemission spectroscopy with an He I resonance line (hν = 21.22 eV) from 10 to 300 K. In the photoemission spectra of
YbInCu4 and YbCdCu4 near the Fermi level (EF)
measured at 10 K, the prominent peak structures due to the
Yb2+ 4f7/2 states are clearly observed at 46 and
31 meV, respectively. The difference of the peak energies
qualitatively reflects that of the Kondo temperatures between
YbInCu4 and YbCdCu4. The peak intensities increase
gradually with decreasing temperature for both compounds. The
amount of enhancement of the Yb2+ 4f7/2 peak
from 50 to 10 K is, however, much stronger for YbInCu4 than
for YbCdCu4, due to an increase of the Yb2+
component followed by the valence transition at Tv = 42 K in
YbInCu4. On the other hand, the Yb2+ 4f7/2
states of YbMgCu4 is observed as a broad structure near
EF in the photoemission spectrum at 10 K. We have also
measured the x-ray photoemission spectra in the Yb 4d core state
region of YbXCu4 from 10 to 300 K. For YbInCu4 and
YbCdCu4, the structures due to the Yb2+ and Yb3+
components are recognized for all temperatures. In
particular, the Yb2+ structure is still observed at 300 K
for YbInCu4. The intensity ratio of Yb2+/Yb3+
increases gradually with decreasing temperature for both
compounds. For YbMgCu4, on the other hand, almost only
Yb2+ structures are observed and little temperature
dependence is detected.
Highly crystalline and smooth 1% Ho3+ doped ZnO microspheres with diameters ranging from 0.5 to 15 μm were synthesized using laser ablation technique. Near band edge whispering gallery mode (WGM) resonances from Ho:ZnO microspheres with a single oscillation route in the UV range are observed with 355 nm excitation. Apart from the significantly enhanced visible WGM resonances associated with intrinsic oxygen vacancy defects by Ho3+ doping, the visible range WGM resonances associated with the Ho3+ 5F5 → 5I8 emission at 629–690 nm are also observed with a 488 nm excitation. The WGMs of Ho3+ f-f emission possess lower threshold and high Q-factor values.
Resonant inverse-photoemission spectra of NiAs-type MnTe have been measured with the tunable photon energy mode at kinetic energies of incident electrons (Ek) in the Mn 3p–3d excitation region. The peak structure at 2.9 eV above the valence-band maximum (VBM) is resonantly enhanced at Ek = 50 eV and is attributed to transitions to d 6 final states with 5 E and 5 T 2 symmetries. The broad structure around 12 eV above the VBM in the spectrum at Ek = 46.5 eV and a shoulder on the higher energy side of the main peak at 2.9 eV in the spectrum at Ek = 50 eV is assigned to [Formula: see text] final states and d6 final states with 3Γ symmetries, respectively, where [Formula: see text] stands for a ligand hole and Γ an irreducible representation.
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