Articles by K. Don Dasitha Gunaratne in JoVE
In Situ SIMS and IR Spectroscopy of Well-defined Surfaces Prepared by Soft Landing of Mass-selected Ions Grant E. Johnson1, K. Don Dasitha Gunaratne1, Julia Laskin1 1Physical Sciences Division, Pacific Northwest National Laboratory Soft landing of mass-selected ions onto surfaces is a powerful approach for the highly-controlled preparation of novel materials. Coupled with analysis by in situ secondary ion mass spectrometry (SIMS) and infrared reflection absorption spectroscopy (IRRAS), soft landing provides unprecedented insights into the interactions of well-defined species with surfaces.
Other articles by K. Don Dasitha Gunaratne on PubMed
Photoelectron Imaging Spectroscopy and Theoretical Investigation of ZrSi The Journal of Chemical Physics. May, 2011 | Pubmed ID: 21639436 The photoelectron spectrum of ZrSi(-) has been measured at two different photon energies: 2.33 eV and 3.49 eV, providing electron binding energy and photoelectron angular distribution information. The obtained vertical detachment energy of ZrSi(-) is 1.584(14) eV. The neutral ground and excited state terms are assigned based on experimental and theoretical results. The ground state of ZrSi is tentatively assigned as a (3)Σ(+) state with a configuration of 1σ(2) 1π(4) 1δ(0) 2σ(1) 3σ(1). A low lying (3)Π(i) neutral excited state is identified to be 0.238 eV (1919 cm(-1)) above the ground state. The anion ground state is designated as a (2)Σ(+) state with a 1σ(2) 1π(4) 1δ(0) 2σ(2) 3σ(1) valence electron configuration. A Franck-Condon (FC) simulation of the photoelectron spectrum has been carried out. For the (3)Σ(+) ← (2)Σ(+) band, theoretically calculated bond lengths and frequencies are used in the FC calculation which give good agreement with experiment, while for the (3)Π(i) ← (2)Σ(+) band, the ZrSi bond length is estimated from the FC spectrum. Comparisons are made with previously published theoretical studies and inconsistencies are pointed out. To the best of our knowledge, this study provides the first spectroscopic information on the transition metal-silicon diatomic, ZrSi.
Investigating the Relative Stabilities and Electronic Properties of Small Zinc Oxide Clusters The Journal of Physical Chemistry. A. Dec, 2012 | Pubmed ID: 23241210 We report a combined experimental and theoretical study investigating small zinc oxide clusters. A laser vaporization source and a time-of-flight (TOF) mass spectrometer are employed to produce and identify anionic clusters in the Zn(n)O(m) (n = 1-6, m = 1-7) size regime. The adiabatic detachment energy (ADE) and vertical detachment energy (VDE) of Zn(3)O(3)(-) and Zn(3)O(4)(-) clusters are determined via anion photoelectron spectroscopy. We have utilized density functional theory (DFT) calculations to explore the possible geometries of neutral and anionic Zn(3)O(m) (m = 3-5) clusters, while the theoretical ADE and VDE values are compared with experimental results. The experimentally observed relative abundances among the Zn(3)O(m)(-) (m = 3-5) clusters are investigated through calculations of the detachment energies, dissociation energies, and HOMO-LUMO gaps. We find that the Zn(3)O(3) cluster maintains enhanced stability compared to their oxygen-rich counterparts. Furthermore, by coupling the experimentally obtained photoelectron angular distributions of Zn(3)O(3)(-) and Zn(3)O(4)(-) with electronic structure calculations, the nature of the highest occupied molecular orbitals is discussed, with the goal of aiding the isolation (ligand-capped)/deposition of these building blocks.
Probing the Valence Orbitals of Transition Metal-silicon Diatomic Anions: ZrSi, NbSi, MoSi, PdSi and WSi Physical Chemistry Chemical Physics : PCCP. Apr, 2013 | Pubmed ID: 23493900 Evolution of electronic properties and the nature of bonding of the 4d-transition metal silicides (ZrSi, NbSi, MoSi and PdSi) are discussed, revealing interesting trends in the transition metal-silicon interactions across the period. The electronic properties of select transition metal silicide diatomics have been determined by anion photoelectron imaging spectroscopy and theoretical methods. The electron binding energy spectra and photoelectron angular distributions obtained by 2.33 eV (532 nm) photons have revealed the distinct features of these diatomics. The theoretical calculations were performed at the density functional theory (DFT) level using the unrestricted B3LYP hybrid functional and at the ab initio unrestricted coupled cluster singles and doubles (triplets) (UCCSD(T)) methods to assign the ground electronic states of the neutral and anionic diatomics. The excited electronic states were calculated by the DFT (TD-DFT)/UB3LYP method. We have observed that the valence molecular orbital configuration of the ZrSi and NbSi anions are significantly different from that of the MoSi and PdSi anions. By combining our experimental and theoretical results, we report that the composition of the highest occupied molecular orbitals shift from a majority of transition metal s- and d-orbital contribution in ZrSi and NbSi, to mainly silicon p-orbital contribution for MoSi and PdSi. We expect these observed atomic scale transition metal-silicon interactions to be of increasing importance with the miniaturization of devices approaching the sub-nanometer size regime.