A5001238689- Astrophysics and Star Formation Studies
- Atmospheric Ozone and Climate
- Advanced Chemical Physics Studies
- Astro and Planetary Science
- Molecular Spectroscopy and Structure
- Spectroscopy and Laser Applications
- Spectroscopy and Quantum Chemical Studies
- Atomic and Molecular Physics
- Ammonia Synthesis and Nitrogen Reduction
- Atmospheric chemistry and aerosols
- nanoparticles nucleation surface interactions
- Isotope Analysis in Ecology
- Environmental DNA in Biodiversity Studies
- Electrostatics and Colloid Interactions
- Microfluidic and Bio-sensing Technologies
- Solid-state spectroscopy and crystallography
- Organic and Molecular Conductors Research
- Fluid Dynamics and Thin Films
- Electron and X-Ray Spectroscopy Techniques
- Quantum, superfluid, helium dynamics
- Light effects on plants
- Surface Modification and Superhydrophobicity
- Origins and Evolution of Life
- Scientific Research and Discoveries
- Phase-change materials and chalcogenides
The Open University
2009-2024
Science and Technology Facilities Council
2008
University College London
2002-2005
Hong Kong Metropolitan University
2005
Lancaster University
1991
In order to understand much of the chemistry that underpins astronomical phenomena (e.g. star and planet formation) it is essential probe physico-chemistry ice surfaces under conditions. The physical properties chemical reactivity such icy depends upon its morphology. Thus necessary explore how morphology astrochemical ices influenced by their local environment temperature pressure) mechanisms which they are processed. this paper we report results a series experiments variety molecular using...
We present the first high resolution vacuum ultraviolet photoabsorption study of amorphous benzene with comparisons to annealed crystalline and gas phase. Vapour deposited layers were grown at 25 K 90 under conditions pertinent interstellar icy dust grains planetary bodies in our solar system. Three singlet-singlet electronic transitions solid correspond 1B2u, 1B1u 1E1u states, redshifted by 0.05, 0.25 0.51 eV respectively respect The symmetry forbidden 1B2u ← 1A1g exhibit vibronic structure...
ABSTRACT The recent detection of ethanolamine (EtA, HOCH$_2$CH$_2$NH$_2$), a key component phospholipids, i.e. the building blocks cell membranes, in interstellar medium is line with an exogenous origin life-relevant molecules. However, stability and survivability EtA molecules under inter/circumstellar Solar System conditions have yet to be demonstrated. Starting from assumption that mainly forms on ice grains, we systematically exposed EtA, pure mixed amorphous water (H$_2$O) ice,...
The authors present the results of a morphological study solid ammonia using both Fourier-transform infrared and vacuum ultraviolet (VUV) spectroscopy. Dramatic changes in VUV spectra at temperatures between 65 85 K provide deeper insight into structure ice particularly with observation an exciton transition 194 nm (6.39 eV) spectrum, revealing that is composed crystallites. A complementary observed IR spectrum 1100 cm(-1) which assigned to symmetric deformation molecules surfaces Such...
Transmission infrared spectroscopy has been used in a systematic laboratory study to investigate hydrogen bonding binary mixtures of CH3OH and H2O, vapour deposited at 30 K, as function CH3OH/H2O mixing ratio, R. Strong intermolecular interactions are evident between H2O with band profiles the ices differing from that pure components changing significantly Consistent evidence O-H C-H detailed analysis C-O stretch reveal two different structural regimes below above R = 0.6-0.7. The solid were...
We present results of a combined vacuum ultraviolet (VUV) and infrared (IR) photoabsorption study amorphous benzene : water mixtures layers to investigate the benzene-water interaction in solid phase. VUV spectra 1 1, 10 100 at 24 K reveal concentration dependent shift energies 1B2u, 1B1u 1E1u electronic states benzene. All bands blueshift from pure towards gas phase with increasing concentration. IR strong dOH-π via dangling OH stretch delocalised π system molecule. Although this influences...
We present experimental measurements of photodesorption from ices astrophysical relevance. Layers benzene and water ice were irradiated with a laser tuned to an electronic transition in the molecule. The translational energy desorbed molecules was measured by time-of-flight (ToF) mass spectrometry. Three distinct processes identified: direct adsorbate-mediated desorption producing temperature around 1200 K, indirect resulting 450 substrate-mediated both temperatures 530 respectively. each...
Carbonic acid (H2CO3) is a weak relevant to astrobiology which, date, remains undetected in space. Experimental work has shown that the beta-polymorph of H2CO3 forms under space conditions through energetic (UV photon, electron, and cosmic ray) processing CO2- H2O-rich ices. We present systematic set VUV photoabsorption spectra pure mixed CO2 H2O ices exposed 1 keV electrons at 20 80 K simulate different interstellar Solar System environments. Ices were then annealed obtain layer which was...
Microsized particles play an important role in many diverse areas of science and technology, for example, surface reactions micron-sized a key astrochemistry, plasma reactors atmospheric chemistry. To date much our knowledge such chemistry is derived from 'traditional' science-based research. However, the large area morphology material commonly used techniques may not necessarily mimic that on micron/nano scale particles. Hence, new generation experiments which spectroscopy (e.g., albedo)...
The nonthermal desorption of water from ice films induced by photon and low energy electron irradiation has been studied under conditions mimicking those found in dense interstellar clouds. Water following at 250 nm relies on the presence an absorbing species within H2O ice, this case benzene. Desorption cross sections are obtained used to derive first order rate coefficients for processes. Kinetic modeling compare efficiencies these mechanisms with others known be operation
Synchrotron radiation is a good mimic of solar and therefore has been widely used to study photo-induced physics chemistry in the terrestrial atmosphere. In this paper we review how synchrotron being as tool for investigating atmospheric with particular emphasis on studies related ozone depletion, global warming ionospheric phenomena. The concludes discussion new possibilities that next generation synchrotron-based light sources will provide.
The kinetic energy of benzene and water molecules photodesorbed from astrophysically relevant ices on a sapphire substrate under irradiation by UV laser tuned to the S1←S0 π→π* transition has been measured using time-of-flight mass spectrometry. Three distinct photodesorption mechanisms have identified—a direct adsorbate-mediated desorption benzene, an indirect water, substrate-mediated both water. translational temperature each desorbing population was well in excess ambient ice matrix.
In this paper we report the results of first experimental study irradiation low temperature water ice (30 and 90 K) using energy (4 keV) 13C+ 13C2+ ions. 13CO2 H2O2 were readily formed within H2O with product yield growth rate observed to be highly dependent on both sample ion charge state.
Spectroscopic studies play a key role in the identification and analysis of interstellar ices their structure. Some molecules have been identified within either as pure, mixed, or even layered structures. Absorption band features water ice can significantly change with presence different types impurities (CO, CO2, CH3OH, H2CO, etc.). In this work, we carried out theoretical investigation to understand behavior frequency, strength impurities. The computational study has supported complemented...
In this paper we present the first study of VUV photoabsorption spectrum condensed phase SO2 recorded over region 120 to 320 nm (10.33 3.64 eV). Distinct spectral features were observed that can be used distinguish between formation amorphous and crystalline ice structures. These signatures may then probe different structures as a function both deposition rate substrate temperature.
Absorption spectra of vacuum-deposited films ammonia have been obtained in the range 115 nm to 310 for a set 15 deposition temperatures, Td, between 20 K and 80 K. Results focus upon region 130 overlapping D, E, F G←X Rydberg transitions involving Wannier-Mott excitons. We identify two phases ammonia, showing solid be polymorphic. Peak absorption wavelengths interest are found shift red by 299 cm-1, Td 50 K, 1380 cm-1 55 Shifts provide evidence presence spontaneously generated electric...
The stoichiometric mixing ratio of CO<sub>2</sub> : NH<sub>3</sub> ices determines both the initial chemical and physical properties their evolution through thermal processing including bonding environment, crystallite size amount residue.
Mud flats, Fejø, Denmark: a 2D representation of defect-free regions in molecular crystal that can support Wannier–Mott excitons.
Molecular oxygen, nitrogen, and ozone have been detected in the Solar System. They are also expected to be present ice-grain mantles within star-forming regions. Laboratory experiments that simulate energetic processing (ions, photons, electrons) of ices essential for interpreting directing future astronomical observations. We provide VUV photoabsorption spectroscopic data energetically processed nitrogen- oxygen-rich will help identify absorption bands and/or spectral slopes observed on icy...
Many experimental parameters determine the chemical and physical properties of interstellar ice analogues, each which may influence molecular synthesis that occurs in such ices. In part 1, James et al., RSC Adv., 2020, 10, 37517, we demonstrated effects stoichiometric mixing ratio had on CO2 : NH3 mixtures impact induced by thermal processing. Here, 2, extend this to include 1 keV electron irradiation at 20 K several ratios ices followed We demonstrate not all form same products. Not only...
Astrochemistry is the study of chemical processes under those conditions prevalent in astronomical environments. Due to temperatures found many astrophysical environments much this chemistry heterogeneous occurring within icy mantles on planetary surfaces, comets and dust grains interstellar medium. The physical properties reactivity such surfaces depends upon its morphology. Thus it necessary explore how morphology astrochemical ices influenced by their local environment (e.g. temperature...