October 2016 Meeting

Speaker: Douglas P. Ridge, Ph.D., University of Delaware

Topic: Fourier transform ion cyclotron resonance studies:  Examples including Infra-red multiphoton dissociation studies of cadmium sulfide metal clusters

Date: Monday, October 17, 2016

Time: 6:15 pm Dinner, 7:15 pm Presentation

Location: Gerstel/Agilent Office, 701 Digital Drive #J, Linthicum Heights, MD 21090 (Directions)

Dinner: Please RSVP to Katherine Fiedler (Katherine.L.Fiedler@fda.hhs.gov) before October 17 if you will be attending the dinner.

Abstract: Fourier transform ion cyclotron resonance mass spectrometry involves injecting ions into an electromagnetic trap where they can be detected and mass analyzed on the basis of their cyclotron frequency.  The method facilitates manipulating the trapped ions in various informative ways.  The reactivity of trapped ions can be examined by exposing the trapped ions to reactive gases.  Structure and spectroscopic properties can be examined by subjecting the trapped ions to collisional or photon induced decomposition.  Examples of the applications of these techniques will be described.  In particular the application of these techniques to the study of Cadmium sulfide metal clusters will be described.  These metal clusters are important in marine environments both as potentially toxic pollutants and in relation to the exotic biology found around hydrothermal vents in the ocean floor.  Although cadmium sulfide is insoluble in water metal sulfide clusters can be prepared by electrospraying soluble metal salts such as cadmium acetate and allowing the resulting cadmium acetate clusters to react with H2S in the ion trap.  This results in clusters containing multiple Cd atoms and bisulfide and sulfide counter ions.  The structure of these clusters have been probed by subjecting them to collision induced decomposition, IR multiphoton dissociation, and density functional theory calculations.  Among the conclusions is that when excited the clusters tend to lose preferentially metal atoms forming a series of clusters containing hypervalent polysulfides.