6830
J. Phys. Chem. 1991,95,6830-6832
In these experiments, parent bandwidths were distinctly increased relative to the argon matrix spectra. Nonetheless, product formation was observed,with several new infrared absorptions. These were slightly shifted from the argon matrix values, but were in general agreement, as can be seen in Table I. However, bands due to the GaC, symmetric and antisymmetric stretching modes could not be conclusively identified. The symmetric stretch would be expected near its 520-cm-I argon matrix position. Unfortunately, in the thin film blank experiments, the symmetric stretching mode of parent TMG was observed weakly due to the inhomogeneous environment. While the band shape was somewhat different in the deposition experiments compared to the blank, no new band could be conclusively identified. The antisymmetric stretch should lie near 565 cm-I, 10 cm-' from the parent band position. However, the parent band width was nearly 20 cm-I (full width at half-maximum), so that a nearby product absorption could not be resolved. Nonetheless, spectra in the AsH3 region provided distinct evidence of complex formation in the thin film,
as would be expected from the matrix results. Conclusions The deposition of mixtures of (CH3)3Gaand ASHpinto inert matrices at 14 K has given rise to the formation of a 1:l molecular adduct. This species was characterized by a number of perturbed vibrational modes, and band assignments were confirmed by isotopic labeling. The structure of the adduct appears to be C , with a distinct distortion of the GaC3 skeleton from planarity. This structure, along with the observed vibrational shifts, are in good agreement with ab initio calculations on the analogous H3GaAsH3 adduct. Evidence was also obtained for the existence of this complex at room temperature, either in the gas phase or possibly in the liquid phase condensed on the windows of the gas cell.
Acknowledgment. The authors gratefully acknowledge support of this research by the National Science Foundation, through grant CHE 90-24474.
Production of Blmetalllc Clusters Containing Manganese Atoms by Laser-Vaporlzatlon Method Yasutomo Sone, Kdyoshi Hosbino, Takashi Naganuma, Atsushi Nakajima, and Koji Kaya* Department of Chemistry, Faculty of Science and Technology, Keio University, 3- 14-1 Hiyoshi, Kohoku- ku, Yokohama 223, Japan (Received: March 19, 1991; In Final Form: April 17, 1991)
Bimetallic clusters containing manganese atoms were generated by applying a laser-vaporization method. The bimetallic clusters composed of Ta and Mn, TanMnm,were produced and could be mixed in any ratio, whereas those composed of Co and Mn, Co,Mn,, could only be produced with more than four cobalt atoms; Co, plays an important role in the production of Co,Mn, clusters. The difference of mass distribution between Ta,Mn, and Co,Mn, can be qualitatively explained by an analogy of their phase diagrams in the bulk.
Introduction nephysical and chemical of metal alloys have long attracted much attention in the field of and new In contrast to the bulk metal alloys, investigation of alloy clusters in the gas phase is a newly expanding field, and properties of several-alloy clusters have been reporfed.l-s Most of'the alloy clusters were generated by evaporating the elements from two separate oven^.^-^ Recently, we have developed a new method for producing alloy clusters by laser vaporization;6two different metal rods are vaporized by two vaporization lasers. The merit of this method is that the mixing ratio of two metal elements can be controlled easily by the fluence of individual lasers. In this paper, we discuss the production mechanism of bimetallic clusters produced by this method. We have applied this method to produce bimetallic clusters containing manganese atoms (Mn). It is generally known that it is hard to produce neutral manganese clusters in itself. This is because the binding energy of Mn2 is (1) Martin, T. P. J . Chem. Phys. 1984,81, 4426; 1985,83,18. (2) Sattler, K. 2.Phys. D 1986, 3, 223. (3) (a) Schild, D.; Pflaum, R.; Sattler, K.; Recknagel. E. J . P h p . Chem. 1987,91,2649. (b) Schild, D.; Pflaum, R.; Riefer, G.; Recknagel, E. 2.Phys. D 1988, IO, 329. (4) Rohlfing, E. A,; Cox, D. M.; Petkovic-Luton. R.;Kaldor, A. J . Phys. Chem. 190488,6221. ( 5 ) (a) Wheeler, R. 0.;LaiHing, K.; Wilwn, W. L.; Allen, J. D.; King, R. B.; Duncan, M. A. J . Am. Chcm. Soc. 1986,108,8101. (b) Wheeler, R. G.; LaiHing, K.; Wilson, W. L.; Duncan, M.A. J . Chcm. Phys. I=, 88, 2831. (6) Nonose, S.;Sone, Y.; Onodcra, K.; Sudo, S.;Kaya, K. J . Phys. Chem.
1990, 94. 2144.
extremely small' and the growth of clusters is prevented. Then, we tried to dope Mn atoms into other metal clusters with the assistance of the binding between Mn and other metal atoms. We mixed manganese atoms with different metal elements, Ta and Co, and their bimetallic clusters could be produced successfully. Experimental Section The experimental apparatus has been described in detail previously.6 Briefly, clusters containing two metal elements were synthesized via laser vaporization of two different target rods by two pulsed YAG lasers (532 nm) in a He carrier gas (5-10 atm). The delay time between the two laser pulses was adjusted to synchronize with the flow speed of the He gas, in order to mix the metal elements homogeneously. The ionic or neutral products were mass-analyzed by a timeof-flight (TOF) mass spectrometer equipped with a reflectron.8 The cluster ions were directly extracted into the TOF tube by applying a fast high-voltage pulse (Velonex Model-350 and V1742) to the extraction bias? and the neutral clusters were ionized by an ArF excimer laser in a static electric field. The ionization-laser fluence was limited to
