Band Structure Effects in Ejection of Ni Atoms in Fine Structure States

He, Chun; Postawa, Zbigniew; Rosencrance, S. W.; Chatterjee, R.; Garrison, B. J.; Winograd, Nicholas

doi:10.1103/physrevlett.75.3950

Cited by 30 publications

(29 citation statements)

References 25 publications

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“…[41][42][43][44] A striking result was the pronounced population inversion of a 3 D 3 and a 3 D 2 sublevels in Ni metastable state, with respect to the electronic ground state. The density ratio a 3 F 4 : a 3 D 3 : a 3 D 2 should be close to 9:7:5 with equal Boltzmann factors.…”

Section: Optical Absorption Measurementsmentioning

confidence: 95%

“…44 More surprisingly, for a single crystal Ni ͑001͒ target under bombardment by 5 keV Ar + ions, the populations of a 3 D 3 and a 3 D 2 were found to be 5.7 and 7.4 times that of a 3 F 4 , respectively. 43 This remarkable disparity in the Ni partition factor could originate either from target crystal structure differences or from differences in experimental techniques. 42,44 In our study, the coil and target were polycrystalline Ni, and the ion sputtering energies were ϳ100 eV on the coil and several hundreds of eV on the Ni target with the power ranging from 40 to 70 W. The energy dependence of low ionenergy Ar + bombardment on the population distributions of sputtered Ni atoms has not been reported; however, we expect that at this lower ion energy, a smaller fraction of Ni metastables could be produced.…”

Section: Optical Absorption Measurementsmentioning

confidence: 99%

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Nickel atom and ion densities in an inductively coupled plasma with an internal coil

Sadeghi

Donnelly

et al. 2007

Journal of Applied Physics

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Section: Optical Absorption Measurementsmentioning

confidence: 95%

Section: Optical Absorption Measurementsmentioning

confidence: 99%

Nickel atom and ion densities in an inductively coupled plasma with an internal coil

Sadeghi

Donnelly

et al. 2007

Journal of Applied Physics

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“…Second, it is very sensitive so that measurements can be made on an effectively undamaged surface. The experimental apparatus, which has been described in more detail previously 13,14 comprises a UHV chamber (base pressure 2.5 Â 10 À10 mbar) equipped with low energy electron diffraction (LEED) as well as an 8 keV Ar ion source which could be operated in either pulsed or continuous mode. A 300 ns pulse of normally incident 8 keV Ar ions, focused to a mm spot on the target, was used to sputter Al or Ni atoms into the path of a ribbon beam from a tunable dye laser.…”

Section: Methodsmentioning

confidence: 99%

Angle and energy distributions of neutral atoms sputtered from Ni3Al(100)

King

Zimmermann

Riederer

et al. 1998

Rapid Commun. Mass Spectrom.

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The energy and angular distributions of Ni and Al atoms sputtered from Ni 3 Al(100) by 8 keV Ar have been measured using multiphoton resonance ionization detection. The Al atoms, which originate entirely from the top atomic layer of Ni 3 Al(100), are predominantly sputtered along close packed <110> directions. On the other hand the sputtered Ni flux, which arises from both the first and second layers, has a large component normal to the surface. Molecular dynamics computer simulations agree well with experimental results and suggest that the normal emission of Ni atoms arises primarily from second-layer atoms. # 1998 John Wiley & Sons, Ltd. Received 24 April 1998; Revised 22 July 1998; Accepted 24 July 1998 Energy transfer processes that lead to the desorption of atoms and molecules from ion bombarded surfaces involve a complex sequence of nuclear collisions. There have been many spirited debates through the years related to questions about the detailed nature of these collisions. Various strategies ranging from energy transport theories 1 to Monte Carlo simulations 2 have been exploited to gain a certain level of understanding. Of special interest is the case of single crystal metal targets where atoms are observed to eject along specific crystallographic directions. For these systems, molecular dynamics (MD) computer simulations have been successful at reproducing experimental measurements of the energy and angle distributions of neutral atoms.3 This agreement is encouraging since comparisons at this level of detail confirm a high degree of reliability for the MD model.One aspect of the desorption process has involved the depth of origin of the ejected atom.1-4 Computer simulations have shown that for copper single crystals b90% of the particles are emitted from the top layer.5 More recent models suggest that for fcc single crystals, some 2 nd layer ejection can occur through a ring of top-layer atoms and is observed primarily at an angle normal to the surface plane.6-8 Experimental tests of this prediction have been difficult since there is no way to distinguish between layers in a monoelemental target. One particularly elegant experiment involved the measurement of the yield of Ru from Ru{0001} as it is systematically covered with a monolayer of Cu. 9 The results show that the particles do arise almost exclusively from the top layer, although no information regarding the take-off angle of the few atoms emitted from the second layer were reported. Moreover, the overlayer of Cu had an undefined relationship to the Ru substrate.Single crystal metallic alloys represent an interesting model system for these types of studies. It is technically feasible to prepare compounds that have well-defined numbers of atoms of a specific type in a specific layer. Moreover, the atomic configurations can be precisely determined using a variety of spectroscopic approaches. [10][11][12] These attributes are critical to designing experiments that can be compared with theory since important input parameters for molecular dynamics...

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“…1 The a 3 D 3 excited metastable state is much more populated than the a 3 F 4 ground state in the flux sputtered from the single crystal of Ni. The population ratio of a 3 D 3 to a 3 F 4 is more than 5.…”

Section: Introductionmentioning

confidence: 99%

Population inversion of metastable Ni atoms sputtered fromNi(100),Ni3Al(100), and
Tan
¹
,
King
²

2006
Phys. Rev. B

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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.

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Band Structure Effects in Ejection of Ni Atoms in Fine Structure States

Cited by 30 publications

References 25 publications

Nickel atom and ion densities in an inductively coupled plasma with an internal coil

Nickel atom and ion densities in an inductively coupled plasma with an internal coil

Angle and energy distributions of neutral atoms sputtered from Ni3Al(100)

Population inversion of metastable Ni atoms sputtered fromNi(100),Ni3Al(100), and
Tan
¹
,
King
²

2006
Phys. Rev. B

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Band Structure Effects in Ejection of Ni Atoms in Fine Structure States

Cited by 30 publications

References 25 publications

Nickel atom and ion densities in an inductively coupled plasma with an internal coil

Nickel atom and ion densities in an inductively coupled plasma with an internal coil

Angle and energy distributions of neutral atoms sputtered from Ni3Al(100)

Population inversion of metastable Ni atoms sputtered fromNi(100),Ni3Al(100), andTan1, King2 2006Phys. Rev. B

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Population inversion of metastable Ni atoms sputtered fromNi(100),Ni3Al(100), and
Tan
¹
,
King
²

2006
Phys. Rev. B