Photoionization and excitation energies of an Al atom in Ar N  clusters

Whetten, Robert L.; Schriver, K. E.; Persson, John L.; Hahn, M. Y.

doi:10.1039/ft9908602375

Cited by 36 publications

(31 citation statements)

References 21 publications

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“…These observations imply that the cobalt atom should be viewed as a reaction site until it is completely covered with germanium atoms. This distribution feature is an evidence16 that the [CoGe 10 ] − cluster has a cage structure. It has been reported that Ge 10 or [Ge 10 ] − does have a cage structure 17,.…”

Section: Resultsmentioning

confidence: 69%

Laser ablation of Co/Ge mixtures: a new type of endohedral structure, a semiconductor cage trapping a metal atom

Zhang

Gao

2001

Rapid Comm Mass Spectrometry

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In experiments on Co/Ge binary clusters by laser vaporization, a remarkably strong signal in the mass spectrum was presented, which was assigned to the cluster anion consisting of ten germanium atoms and one cobalt atom, [CoGe 10 ]À . For this cluster anion we suggest an endohedral structure ± aGe 10 cage trapping a Co atom in its interior. Reactions between cobalt clusters and germanium clusters using a laser double ablation reactor also confirmed the endohedral structure. The fact that an atom or a group of atoms can be trapped in a fullerene cage 1,2 has been generally recognized since 1991 when techniques to produce metallofullerene were developed 3,4 and the samples were produced in bulk. This provided the conditions to directly study the characteristics of a metallofullerene, 4 and consequently numerous experimental explorations of endohedral fullerenes were conducted. Theoretical studies on the structures and the formation mechanism 5,6 of the new complexes were also developed. But for almost a decade, most of the species with endohedral structures produced and studied mainly had carbon fullerene cages. 7±13 Recently, a W-encapsulating Si 12 cage cluster was reported. 14 Here we give a new experimental result, which might indicate that a transition metal atom (Co) was trapped in a semiconductor cage (Ge 10 ). This recognition comes from the analysis of mass spectra of Co/ Ge binary cluster anions produced by laser ablation and also from the reactions between cobalt clusters and germanium clusters in a laser double ablation reactor (LDAR). EXPERIMENTALThe binary cluster anions of germanium and cobalt were generated and analyzed under the following conditions. The samples were prepared with germanium (purity 99.99%) and cobalt (purity 99.9%) powders, mixed well in different atomic ratios and pressed to form tablets. The experiments to produce and detect Co/Ge binary cluster anions were performed by a vaporization laser and the first stage of a home-made tandem time-of-flight mass spectrometer (T-TOFMS). A detailed description of the T-TOFMS is given elsewhere. 15 In our experiments the first stage of the T-TOFMS is only used to produce the clusters. Briefly, the second harmonic of a Q-switched Nd: YAG laser (532 nm, 10 mJ/pulse, 10 pulse/s) was focused on the surface of a tablet sample held in the vacuum chamber (at 10 À6 Torr) of the spectrometer to produce the cluster anions. The produced cluster anions were extracted and accelerated with a pulse voltage of À1.2 kV, and then drifted in a fieldfree region 3.5 m long. The anions were detected by a dual micro-channel plate detector held in the end of the field-free region, and recorded to give the mass spectrum. Typically, 1000±2000 laser shots were accumulated and stored in an IBM-PC computer.

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Section: Resultsmentioning

confidence: 69%

Laser ablation of Co/Ge mixtures: a new type of endohedral structure, a semiconductor cage trapping a metal atom

Zhang

Gao

2001

Rapid Comm Mass Spectrometry

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“…The ablation laser is a Nd:YAG laser (A 1064 nm, pulse duration 10 ns, repetition rate 12.5 Hz) with an output energy of 10-100 mJ/pulse. The noble gas is expanded from a pulsed nozle (diameter 0.8 nm, backing pressure [2][3][4][5][6][7][8] bar, room temperature) and is mixed with the metal ions contained in the plasma plume at 0.5-5 mm away from the nozzle orifice. The cluster ions produced from this mixing are then analyzed with a Timeof-Flight (TOF) device, which can be used either as a linear or as a reflectron spectrometer.…”

Section: Methodsmentioning

confidence: 99%

Ion‐Size Effects in the Growth Sequences of Metal‐Ion‐Doped NobleGas Clusters

1997

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We have studied the stability and the structure of doped noble gas cluster ions of the type M+Xn, (M=In, Al, Na, X=Ar, Kr, Xe) by systematically changing the composition M/X and observing changes in the magic number patterns appearing in the mass spectra. When the metal ion radius is comparable to the radius of the noble gas atom, the mass spectra show the familar icosahedral magic numbers n+ 1=13,19,23,26,29,32, 46, 55,... In constrast, for metal ions with radii significantly smaller than the noble gas atoms, we observe a new series of magic numbers n + 9, 11, 17, 21,24, 26,... This series converts into the icosahedral one for larger clusters. Using a simple hard sphere packing model, we show that this new series of magic numbers is consistent with a cluster growth sequence which is based on a capped square antiprism (CSA) geometrical structure of the clusters.

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“…[3][4][5][6][7][8][9][10] While complexes of the heavier atoms in this group ͑Ga, 11 In, 12,13 Tl 14,15 ͒ have also been investigated, those involving aluminum have received the most attention. [16][17][18][19][20][21][22] Gardiner and Lester 16 reported the first observation of the AlAr complex using resonance enhanced multiphoton ionization ͑REMPI͒ through the B 2 ⌺ ϩ -X 2 ⌸ 1/2 electronic transition, which correlates with the Al atomic 4s←3p transition. Callender et al 17 reported laser fluorescence excitation spectra of the complexes of Al with the heavier noble gases, and employed resolved emission spectra to characterize the vibrational spacings in the ground electronic states of AlAr, AlKr, and AlXe.…”

Section: Introductionmentioning

confidence: 99%

“…23 The dependence on the number of ligands n of the electronic transitions in AlAr n clusters correlating with the Al 4s←3 p and 3d ←3p atomic transitions has been investigated with mass resolved REMPI detection. 19,24 Despite the considerable attention given to aluminum atom complexes, to our knowledge no previous report of the observation of the AlNe complex has been published. Metal-neon complexes are expected to have very small binding energies.…”

Section: Introductionmentioning

confidence: 99%

Experimental and theoretical study of the AlNe complex

Yang

Dagdigian

Alexander

1998

The Journal of Chemical Physics

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Experimental and theoretical studies of the CN-Ar van der Waals complexExperimental detection and theoretical characterization of the H 2 -NH ( X ) van der Waals complexThe laser fluorescence excitation spectrum of the AlNe complex, in the vicinity of the Al atomic 3d←3p and 5s←3p atomic transitions, is reported. Transitions out of the vϭ0 vibrational levels of both lower-state spin-orbit levels, X 1 2 ⌸ 1/2 and X 2 2 ⌸ 3/2 , to vibrational levels of the C 2 ⌬, D 2 ⌸, and H 2 ⌺ ϩ AlNe electronic states were observed. From observations of the onset of excitation to the Al(3d)ϩNe dissociation continuum, dissociation energies for the various AlNe electronic states were determined. Ab initio calculations of AlNe electronic states correlating with the ground Al(3p)ϩNe atomic asymptote were also carried out. The X 1 2 ⌸ 1/2 and X 2 2 ⌸ 3/2 binding energies computed using the calculated AlNe͑X 2 ⌸, A 2 ⌺ ϩ ͒ potential energy curves were in reasonable agreement with the experimental determinations. The experimentally determined dissociation energy for the X 2 2 ⌸ 3/2 level is significantly larger than that of the ground X 1 2 ⌸ 1/2 level ͑D 0 ϭ32.3Ϯ0.3 and 14.1Ϯ0.3 cm Ϫ1 , respectively͒.

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Photoionization and excitation energies of an Al atom in Ar N clusters

Cited by 36 publications

References 21 publications

Laser ablation of Co/Ge mixtures: a new type of endohedral structure, a semiconductor cage trapping a metal atom

Laser ablation of Co/Ge mixtures: a new type of endohedral structure, a semiconductor cage trapping a metal atom

Ion‐Size Effects in the Growth Sequences of Metal‐Ion‐Doped NobleGas Clusters

Experimental and theoretical study of the AlNe complex

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