Metastable helium a 3 Σ + u molecules are produced in helium nanodroplets by electron bombardment, and become attached to their surface. Photo induced electronic transitions release them, and they are subsequently detected when they eject secondary electrons upon reaching a nearby surface. We report here the first high resolution spectroscopic study of this system. It reveals a highly non-thermal rotational state distribution with N = 1 and 11 ≤ N ≤29 populated but with the intermediate N states missing. Further studies of the bombarding electron energy appearance threshold for the high rotational states suggest that their precursor is the atomic 2 3 P state.PACS. 36.40.Vz Optical properties of clusters -67.40.Yv Helium impurities and other defects
In this article, we present data on the critical dependence of the magnetic, electrical and microstructural properties of spin-valves (SV) on seed-layer thicknesses. The SV structure is: seed-layer/PtMn 140 A/CoFe 16 A/Ru 8.5 A/CoFe 21 A/Cu 20 A/CoFe 12 A/NiFe 30 A/Ta 30 A, where the seed layer is NiFeCr-CoFe or NiFeCr/NiFe. As the thickness of the bilayer seed layer is varied, it is found that a critical thickness boundary exists across which the film properties are radically different. The GMR ratio increased from 7% to 14% (a 100% change), the sheet resistance decreased by about 4 ohms/square and the crystalline texture transitioned from weak to extremely strong (111) texture. The critical thickness boundary is at a combined thickness of 37 A to 40 A. These results suggest a mechanism at the boundary between NiFeCr and CoFe during film growth. A better lattice match between NiFeCr-CoFe, for example, NiFeCr 33 A and CoFe 7 A, generates a strong (111) texture, which enhances the MR% as compared to NiFeCr 33 A/CoFe 6 A. The H 50 (the field at 50% MR) also exceeds 2000 Oe. This also indicates enhancement of the PtMn fcc to fct transition based on the specifically combined thicknesses of NiFeCr-CoFe. With the NiFeCr-NiFe seed layer, the critical thickness effect is not observed within these thickness ranges.
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