The significance of autoionization processes during nonresonant one-color two-photon ionization of neutral silver and copper atoms at λ = 248 nm

Franzreb, Klaus; Fine, Joseph

doi:10.1016/0168-583x(93)95937-z

Cited by 2 publications

(2 citation statements)

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“…It is clear that the mechanism of two-photon NRMPI of copper atoms at 248 nm is still an open question. Many suggestions have been offered for what appears to be an enhancement in the NRMPI probability: they include dimers [52], the possibility of a quasi-resonant ionization via the Cu ( 4 D 3/2 ) state which is 249.2 nm above the ground state, shifting and broadening of the energy level in the intense photon field or the possibility of a resonance-enhanced ionization of a 3d electron to an autoionization state [17]. The measurement of normal NRMPI characteristics of N = 2 for thermally generated copper [16], would seem to support the idea that sputtered copper atoms which are either not single atoms or not in the ground state may make significant, even dominant, contributions to the NRMPI signal.…”

Section: Non-resonant Multiphoton Ionizationmentioning

confidence: 99%

“…Non-resonant multiphoton ionization of sputtered neutrals can be a highly sensitive and non-species-specific technique [14,15]. Although the general uniformity of ionization efficiency of sputtered multicomponent neutral particles is still being debated [16,17], the technique has proved to be the most efficient when compared to other methods.…”

Section: Introductionmentioning

confidence: 99%

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Energy distributions of copper ions and atoms sputtered by atomic and molecular ions

Wang¹,

Nor²,

Graham

1997

J. Phys. D: Appl. Phys.

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Non-resonant multiphoton ionization combined with quadrupole and time-of-flight analysis has been used to study sputtering by both atomic and molecular ion beams. The mass spectra and energy distributions of both sputtered atoms and secondary ions produced by 3.6 keV , , , and ion bombardment at to a polycrystalline copper target have been measured. The energy distributions of the copper ions and atoms are found to be different and quite complex. The ion distributions can generally be described by a linear collision cascade model, with possible evidence for a knock-on contribution. The sputtered atom distributions are partially described by a combination of linear collision cascade and dense cascade (thermal spike) models. This is interpreted as support for a time-evolving sputtering mechanism.

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Section: Non-resonant Multiphoton Ionizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Energy distributions of copper ions and atoms sputtered by atomic and molecular ions

Wang¹,

Nor²,

Graham

1997

J. Phys. D: Appl. Phys.

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Energetic ion bombardment of Ag surfaces by C₆₀⁺ and Ga⁺ projectiles

Sun

Szakal

Winograd

et al. 2005

J. Am. Soc. Mass Spectrom.

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The ion bombardment-induced release of particles from a metal surface is investigated using energetic fullerene cluster ions as projectiles. The total sputter yield as well as partial yields of neutral and charged monomers and clusters leaving the surface are measured and compared with corresponding data obtained with atomic projectile ions of similar impact kinetic energy. It is found that all yields are enhanced by about one order of magnitude under bombardment with the C 60 ϩ cluster projectiles compared with Ga ϩ ions. In contrast, the electronic excitation processes determining the secondary ion formation probability are unaffected. The kinetic energy spectra of sputtered particles exhibit characteristic differences which reflect the largely different nature of the sputtering process for both types of projectiles. In particular, it is found that under C 60 ϩ impact (1) the energy spectrum of sputtered atoms peaks at significantly lower kinetic energies than for Ga ϩ bombardment and (2) the velocity spectra of monomers and dimers are virtually identical, a finding which is in pronounced contrast to all published data obtained for atomic projectiles. T he elucidation of the mechanism of interaction of energetic polyatomic or cluster ions with surfaces is of current interest since these projectiles are now being extensively employed as desorption probes in secondary ion mass spectrometry (SIMS) experiments [1,2]. Because of their propensity to produce higher molecular ion signals than corresponding atomic ions and the emergence of commercially available C 60 ϩ [3,4] and Au 3 ϩ [5, 6] ion guns, applications have expanded dramatically. For example, these sources can be focused onto the sample with a probe size about 1 micron, allowing greatly improved molecule-specific imaging experiments. The high secondary ion yield associated with the cluster/solid interaction also allows for molecular depth profiling studies without the accompanying damage accumulation normally associated with atomic bombardment [7][8][9][10][11][12][13][14][15][16][17].The mechanisms associated with the observed secondary ion yield enhancement are not yet clear, although details are emerging quickly. A basic question that must be resolved is to determine whether the yield enhancement occurs as a consequence of increased ionization efficiency, or is due to more effective sputtering in the neutral desorption channel. There is mixed information about this point. For In and Ag surfaces, for example, it has been shown that the enhanced secondary ion yield under SF m ϩ bombardment (m ϭ 1-5) largely arises from the enhanced ionization efficiency attributable to implanted F atoms [18]. For organic systems, however, very high removal rates of neutral species have been reported [2], obviating the need to invoke enhancement of the secondary ionization probability. Most recently, yields and velocity distributions were measured for In and In 2 sputtered from In surfaces bombarded with Au ϩ , Au 2 ϩ , and Au 3 ϩ [19]. Although these experiments do not ad...

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The significance of autoionization processes during nonresonant one-color two-photon ionization of neutral silver and copper atoms at λ = 248 nm

Cited by 2 publications

References 52 publications

Energy distributions of copper ions and atoms sputtered by atomic and molecular ions

Energy distributions of copper ions and atoms sputtered by atomic and molecular ions

Energetic ion bombardment of Ag surfaces by C₆₀⁺ and Ga⁺ projectiles

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The significance of autoionization processes during nonresonant one-color two-photon ionization of neutral silver and copper atoms at λ = 248 nm

Cited by 2 publications

References 52 publications

Energy distributions of copper ions and atoms sputtered by atomic and molecular ions

Energy distributions of copper ions and atoms sputtered by atomic and molecular ions

Energetic ion bombardment of Ag surfaces by C60+ and Ga+ projectiles

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Energetic ion bombardment of Ag surfaces by C₆₀⁺ and Ga⁺ projectiles