Laser ablation generation of arsenic and arsenic sulfide clusters Zbyne ˇk S ˇ palt a , Milan Alberti b, * , Eladia Pen ˜ a-Me ´ndez a,1 , Josef Havel a a Department of Analytical Chemistry, Faculty of Science, Masaryk University, Kotla ´r ˇska ´ 2, 611 37 Brno, Czech Republic b Laboratory of Plasma Physics and Plasma Sources, Faculty of Science, Masaryk University, Kotla ´r ˇska ´ 2, 611 37 Brno, Czech Republic Received 8 February 2005; accepted 10 March 2005 Available online 31 May 2005 Abstract Arsenic clusters As n (n =27) were generated from elemental arsenic using laser ablation on a commercial matrix assisted laser desorption ionization – time of flight (MALDI-TOF) mass spectrometric instrument. Singly charged As n þ clusters were observed only in the positive linear and/or reflectron mode. Negatively charged As n  species were not detected. The confirmation of cluster stoichiometries was done using isotopic pattern modelling. In spite of the high purity of arsenic (99.997%) several arsenic oxides and sulfides were observed during the laser ablation of the pure element. The formation of high clusters of arsenic (n = 20, 60) suggested from quantum chemistry calculations was not proved under the experimental conditions used. Additionally, commercially available As 2 S 2 , As 2 S 3 , As 2 S 5 sulfides and/or arsenic-sulfur mixtures were studied as precursors for the generation of new As n S m clusters. Var- ious arsenic sulfide ions (both negative and positive) were generated and identified: AsS, AsS 3 , As 2 S, As 2 S 2 , As 2 S 3 , As 2 S 5 , As 3 S, As 3 S 2 , As 3 S 3 , As 3 S 4 , As 3 S 5 , As 3 S 6 , As 3 S 7 , As 4 S 3 , As 4 S 4 , while nine species (AsS 2 , AsS 4 , AsS 5 , AsS 6 , AsS 7 , AsS 8 , As 2 S 4 , As 2 S 6 , As 2 S 7 ) were described for the first time. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Arsenic; Sulfur; Arsenic clusters; Arsenic sulfides; Laser ablation synthesis; TOF mass spectrometry 1. Introduction Arsenic and its compounds have been of interest for a long time as a pigment as well as being one of the ele- ments studied extensively by alchemists. Today, the application for arsenic is as a modifier of the mechanical properties of lead and copper alloys and as an additive to eliminate unwanted coloration of glass. The techno- logical use of arsenic as passive layers in the semicon- ductor industry is well known. Arsenic and arsenic compounds are toxic and mobile in the environment [1,2], their concentrations in the environment are con- trolled by strict guidelines [3] and ions of arsenic attack the –SH groups present in enzymes and alter their func- tions [4]. There are many applications of arsenic and arsenic compounds in electronics including the application of arsenic sulfides as optical fibers [5,6]. For example, pulsed laser ablation provides a promising method for thin film deposition applications. Mass spectrometry with a sufficiently high resolution, enabling the observa- tion of isotopic patterns of peaks, can be a powerful tool for the identification of the morphology of the deposited thin layers. Arsenic forms clusters and there are a great number of theoretical studies on the structure of arsenic clusters performed with the help of quantum chemistry methods, the most used approach in the theoretical studies is now the density functional theory (DFT) [7] and the ab initio 0277-5387/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2005.03.089 * Corresponding author. Tel.: +420 5 41 129 344 026; fax: +420 5 41 211 214. E-mail address: alberti@chemi.muni.cz (M. Alberti). 1 On leave from: Department of Analytical Chemistry, Nutrition and Food Science, University of La Laguna, 38071 La Laguna, Tenerife, Spain. www.elsevier.com/locate/poly Polyhedron 24 (2005) 1417–1424