DPS/CEPSAR Seminar Series
When: Friday 23 November 2012 at 2.00pm
Where: Gass Building Seminar Room
Speaker: Sven P.K. Koehler (School of Chemistry and Photon Science Institute, The University of Manchester)
Title: From Gas-phase to Surface Dynamics using Velocity Map Imaging
Abstract:
Velocity Map Imaging (VMI) has become one of the most powerful techniques in the area of gas-phase reaction dynamics;(1) recently, a few groups have also started to employ the VMI technique to study the dynamics of surface reactions.(2) VMI is capable of recording the translational and internal energy distribution of gas-phase fragments simultaneously while at the same time being mass-selective.
Chloroform, CHCl3, is used as a solvent in chemistry, has a history as an anaesthetic, and is photolytically converted into phosgene in the atmosphere by UV radiation. We performed photodissociation studies of chloroform in the gas-phase which allow the dynamics of this process to be unraveled. We also employed photodissociation studies of NO2 to validate Velocity Map Imaging conditions over large volumes for the first time to test the suitability of VMI for surface studies. Finally, surface desorption and scattering studies using VMI will be presented, and the advantages of the different approaches discussed.
(1) A. T. J. B. Eppink, D. H. Parker, Rev. Sci. Instrum. 68, 3477 (1997).
(2) S. P. K. Koehler, Y. Ji, D. J. Auerbach, and A. M. Wodtke, Phys. Chem. Chem. Phys. 11, 7540 (2009); J. R. Roscioli, D. J. Nesbitt, Faraday Discuss. 150, 471 (2011); M. G. White, BNL, personal communication.
Refreshments will be available from 1.45pm.
DPS/CEPSAR Seminar Series
When: Thursday 20 September 2012 at 2.30pm
Where: Robert Hooke Building Seminar Room
Speaker: Dr Jean Christophe Pouilly (CIMAP-GANIL, Caen)
Title: Interaction of biologically-relevant molecular systems with atomic ions and electrons in the gas phase
Abstract:
In cancer treatments involving irradiation of malignant cells by photons, protons or heavy ions like Carbon, a number of secondary particles are produced along the track of the primary particle. Among them, electrons and ions with keV kinetic energy can induce significant damage to DNA and other biological molecules. Therefore, it is of particular importance to investigate the physics and chemistry of this damage at the molecular scale.
In Caen, we study the interaction between neutral biologically-relevant molecular systems in the gas phase and keV kinetic energy atomic ions by means of mass spectrometry. These last years, we focused on building blocks of DNA and proteins: nucleobases and amino acids. In particular, we compared the case of the isolated molecule with that of the molecule embedded in a cluster, to obtain the effect of a molecular environment. In this talk, I will highlight our recent experiments on the nucleobase Adenine that we studied isolated, in pure Adenine clusters, in pure hydrated clusters, and in mixed Adenine-Thymine clusters. We obtained several evidences for the protonation of Adenine induced by the interaction with atomic ions. Such behavior has already been observed after the absorption of photons 1-3 as well as after collisions with electrons 2. In the case of beta-amino acid clusters, a striking result is the formation of peptide ions. I will also present our work in collaboration with the group of Steen Brønsted Nielsen in Aarhus, which pioneered the Electron Capture Induced Dissociation (ECID) of peptide cations. Very recently, we investigated the influence of non-covalently binding acetonitrile and 18-Crown-6 ether to aromatic tripeptides on their ECID patterns, and found dramatic differences.
(1)Barc, B.; Cahillane, P.; Mason, N. J.; Eden, S. 2011. (2) Kim, N. J.; Kang, H.; Jeong, G.; Kim, Y. S.; Lee, K. T.; Kim, S. K. Journal of Physical Chemistry A 2000, 104, 6552. (3) Gador, N.; Samoylova, E.; Smith, V. R.; Stolow, A.; Rayner, D. M.; Radloff, W.; Hertel, I. V.; Schultz, T. The Journal of Physical Chemistry A 2007, 111, 11743.
Refreshments will be available from 2pm.
CEPSAR Seminar Series
When: Thursday 13 September 2012 at 2.30pm
Where: Robert Hooke Building Seminar Room
Speaker: Dr Peter Hoppe (Max Planck Institute for Chemistry, Mainz, Germany)
NanoSIMS Studies on Dust from Supernovae
Abstract:
Primitive Solar System materials contain small quantities of so-called presolar grains that formed in the winds of evolved stars and in the ejecta of stellar explosions. Laboratory studies of these pristine samples have provided a wealth of astrophysical information, such as on stellar nucleosynthesis and evolution, dust formation around stars, processing of dust in the interstellar medium, and formation of our Solar System. An important measurement technique is Secondary Ion Mass Spectrometry (SIMS) which permits to do isotope studies at the sub-micrometer scale. In this talk I will focus on isotope measurements on presolar silicon carbide and silicate grains from supernovae (SNe), done with the NanoSIMS ion probe at the Max Planck Institute for Chemistry. I will present results for selected elements and will discuss implications for SN nucleosynthesis, Galactic chemical evolution, and mixing and molecule chemistry in SN ejecta.
Coffee will be available from 2pm.
Figure: A presolar SiC grain from a supernova. Scale bar is 200 nm.
DPS/CEPSAR Seminar Series
When: Monday 3 September 2012 at 2.30pm
Where: Robert Hooke Seminar Room
Speaker: Professor Olivier Mousis
Title: Formation conditions of icy planetesimals in the primitive nebula: implications for the composition of the outer Solar System
Abstract:
Formation scenarios of the solar nebula invoke two main reservoirs of water ice that may have taken part concurrently into the production of solids. In the first reservoir, which is located within the heliocentric distance of 30 AU, water ice infalling from the Interstellar Medium (ISM) initially vaporized into the hot inner part of the disk and condensed in its crystalline form during the cooling of the solar nebula. The second reservoir, located at larger heliocentric distances, is composed of water ice originating from ISM that did not suffer from vaporization when entering into the disk. In this reservoir, water ice remained mainly in its amorphous form. From these considerations, we discuss here the trapping conditions of volatiles in planetesimals produced within the outer solar nebula and their implications for the origin and composition of gas giant planets, their surrounding satellite systems and comets. In particular, we show that the formation of icy planetesimals agglomerated from clathrate hydrates in the solar nebula can explain in a consistent manner the volatiles enrichments measured at Jupiter and Saturn, as well as the composition of Titan's atmosphere.
Coffee will be available from 2pm.
Image: NASA