Population inversion of metastable Ni atoms sputtered fromNi(100),Ni3Al(100), and

Ming Tan

¹

,

B.V. King

²

Abstract

We have measured the ratio of the population of Ni neutral atoms sputtered into the a 3 D 3 metastable state to that into the a 3 F 4 ground state using two-color ionization schemes. The ratio is 2.27± 0.31 for Ni, 2.34± 0.17 for Ni 3 Al, and 2.61± 0.27 for NiAl. Within experimental error, we observed no effect of the valence band electron structure on the population ratio. We suggest that sputtered atoms should experience resonant neutralization and nonradiative relaxation. Before neutralization, departing Ni ions from the surface have an electron configuration of 3d 9 or 3d 8 4s 1 . The 4s electron orbital of the departing ions captures a valence electron and formed nascent Ni atoms in the D ͑3d 9 4s 1 ͒ and F ͑3d 8 4s 1 ͒ states, respectively. The population inversion can be attributed to the character of ions and atoms of Ni. Because of the character of Ni ions, most of the ejected nascent Ni atoms are in the D state. The character of Ni atoms leads to a low relaxation rate of the D to F state. Many of the nascent Ni atoms in the D state can survive and so the population inversion was observed.

Characterization of the surface film on Zr-based bulk metallic glass using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM)

“…The Standard Electrode Potential is −1.66 V for the reaction Al 3+ + 3e − ↔ Al(s) [16], and −0.25 V for the reaction Ni 2+ + 2e − ↔ Ni(s) where (s) represents solid. Tan and King have studied the population, angular and time-of-flight mass spectra of Al and Ni neutral atoms sputtered from the surfaces of Ni(1 0 0) and NiAl(1 1 0) single crystals under a ultra high vacuum (UHV, the base pressure of chamber is 1.5 × 10 −9 mbar) [17][18][19][20] and found during the study that the NiAl(1 1 0) surface is easier to get oxidized than the Ni(1 0 0) surface. (The gas molecules in the UHV chamber consist mainly of H 2 and H 2 O, and the oxidation is due to the interaction of the Ni(1 0 0) and Ni(1 1 0) surfaces with H 2 O) We therefore believe that the reason why the NiAl(1 1 0) surface is easier to get oxidized than Ni(1 1 0) is the preferential (easier) oxidation of Al metal atoms in the NiAl alloy.…”

Angular distributions of atoms sputtered from NiAl{110} and Ni{100}

“…We have previously reported studies on the population distribution and time-of-flight mass spectra of Al and Ni atoms sputtered from Ni{1 0 0}, NiAl{1 1 0} and Ni 3 Al{1 0 0} [15][16][17]. These studies show that electronic processes, occurring during sputtering, play an important role in determining the population distribution and shaping time-of-flight mass spectra of sputtered atoms.…”