A5006031851- Astrophysics and Star Formation Studies
- Atmospheric Ozone and Climate
- Astro and Planetary Science
- Molecular Spectroscopy and Structure
- Advanced Chemical Physics Studies
- Planetary Science and Exploration
- Spectroscopy and Laser Applications
- Space Exploration and Technology
- Stellar, planetary, and galactic studies
- Astronomical Observations and Instrumentation
- High-pressure geophysics and materials
- Advanced Combustion Engine Technologies
- Scientific Research and Discoveries
- Atmospheric chemistry and aerosols
- Phase Equilibria and Thermodynamics
- Spaceflight effects on biology
- Geology and Paleoclimatology Research
- Superconducting Materials and Applications
- Methane Hydrates and Related Phenomena
- Spacecraft and Cryogenic Technologies
- Particle accelerators and beam dynamics
- Particle Accelerators and Free-Electron Lasers
- Astronomy and Astrophysical Research
- Material Dynamics and Properties
- Radiation Detection and Scintillator Technologies
The Open University
2016-2025
University of Strathclyde
2005-2017
Milton Keynes Hospital
2014
Hong Kong Metropolitan University
2014
National Astronomical Observatories
2013
Chinese Academy of Sciences
2013
Scottish Universities Physics Alliance
2006-2012
Alliance University
2011-2012
Leiden University
1997-2006
Leiden Observatory
1997-2006
Geometrically systematic arrangements of uniform spheres are searchingly investigated in Part I. The relationships disclosed, important wherever orderly distribution points or particles is involved, here especially treated as the underlying principles porosity and permeability. Besides packings denned respectively "chaotic," "haphazard," "chance," six cases simple, packing recognized; two orientation variants, but four independent include hitherto described: "loosest" "tightest." Striking...
With the goal to study physical and chemical evolution of ices in solar-mass systems, a spectral survey is conducted sample 41 low luminosity YSOs using 3-38 um Spitzer ground-based spectra. The long-known 6.0 6.85 bands are detected toward all sources, with Class 0-type showing deepest ever observed. In almost sources band deeper than expected from bending mode pure solid H2O. depth shape variations remaining 5-7 absorption indicate that it consists 5 independent components, which, by...
This paper presents Spitzer-IRS spectroscopy of the CO2 15.2 micron bending mode toward a sample 50 embedded low-mass stars in nearby star-forming clouds, taken mostly from ``Cores to Disks (c2d)'' Legacy program. The average abundance solid relative water protostellar envelopes is 0.32 +/- 0.02, significantly higher than that found quiescent molecular clouds and massive star forming regions. It decomposition all observed profiles requires minimum five unique components. Roughly 2/3 ice...
Medium resolution () VLT-ISAAC M-band spectra are presented of 39 young stellar objects in nearby low-mass star forming clouds showing the stretching vibration mode solid CO. By taking advantage unprecedentedly large sample, high S/N ratio and spectral resolution, similarities ice profiles from source to identified. It is found that excellent fits all can be obtained using a phenomenological decomposition CO profile at into 3 components, centered on , with fixed widths 3.0, 3.5 respectively....
Water (H2O) ice is an important solid constituent of many astrophysical environments. To comprehend the role such ices in chemistry and evolution dense molecular clouds comets, it necessary to understand freeze-out, potential surface reactivity desorption mechanisms systems. Consequently, there a real need from within astronomical modelling community for accurate empirical data pertaining these processes. Here we give first results laboratory programme provide data. Measurements thermal H2O...
The adsorption and desorption of CO on from amorphous H2O ice at astrophysically relevant temperatures has been studied using temperature programmed (TPD) reflection-absorption infrared spectroscopy (RAIRS). Solid is able to diffuse into the porous structure as low 15 K. When heated, a phase transition between two forms occurs over 30-70 K range, causing partial collapse pores entrapment CO. Trapped released during crystallization film. This behavior may have significant impact both...
At the high densities and low temperatures found in star-forming regions, all molecules other than H2 should stick on dust grains timescales shorter cloud lifetimes. Yet these clouds are detected millimeter lines of gaseous CO. temperatures, thermal desorption is negligible, hence a nonthermal mechanism necessary to maintain gas phase. Here first laboratory study photodesorption pure CO ice under ultra-high vacuum conditions presented, which gives rate 3 × 10-3 per UV (7-10.5 eV) photon at...
The desorption characteristics of molecules on interstellar dust grains are important for modelling the behaviour in icy mantles and, critically, describing solid-gas interface. In this study, a series laboratory experiments exploring three small from astrophysically relevant surfaces presented. CO, O2 and CO2 at both sub-monolayer multilayer coverages was investigated non-porous water, crystalline water silicate surfaces. Experimental data modelled using Polanyi-Wigner equation to produce...
Protostars contain icy ingredients necessary for the formation of potential habitable worlds, therefore, it is crucial to understand their chemical and physical environments. This work focused on ice features towards binary protostellar system Ced 110 IRS4A IRS4B, separated by 250 au observed with James Webb Space Telescope (JWST) as part Early Release Science (ERS) Ice Age collaboration. study aimed at exploring JWST observations IRS4B primarily unveil quantify inventories these sources....
Millimeter observations of pre- and protostellar cores show that the abundances gas-phase tracer molecules, C18O N2H+, anticorrelate with each other often exhibit "holes" where density is greatest. These results are reasonably reproduced by astrochemical models, provided ratio between binding energies N2 CO, RBE, taken to be 0.5 0.75. This Letter first experimental report desorption CO from layered mixed ices at temperatures relevant dense cores, studied under ultrahigh vacuum laboratory...
We present Temperature Programmed Desorption (TPD) experiments of CO and N2 ices in pure, layered mixed morphologies at various ice "thicknesses" abundance ratios as well simultaneously taken Reflection Absorption Infrared Spectra (RAIRS) CO. A kinetic model has been developed to constrain the binding energies both pure environments derive kinetics for desorption, mixing segregation. For desorption occurs a single step whereas it proceeds two steps, one corresponding from environment...
The formation of CO2 in quiescent regions molecular clouds is not yet fully understood, despite having an abundance around 10-34 % H2O. We present a study the via non-energetic route CO + OH on non-porous H2O and amorphous silicate surfaces. Our results are form temperature-programmed desorption spectra produced two experimental routes: O2 H O3 H. maximum yield 8 with respect to starting quantity CO, suggesting barrier OH. rate reaction, based modelling results, 24 times slower than model...
The 4.62 μm (2164.5 cm-1) "XCN" band has been detected in the M-band spectra of 34 deeply embedded young stellar objects (YSO's), observed with high signal-to-noise and spectral resolution VLT-ISAAC spectrometer, providing first opportunity to study solid OCN- abundance toward a large number low-mass YSO's. It is shown unequivocally that at least two components, centred 2165.7 cm-1 (FWHM = 26 2175.4 15 cm-1), underlie XCN band. Only 2165.7-component can be ascribed OCN-, strongly...
Solid O2 has been proposed as a possible reservoir for oxygen in dense clouds through freeze-out processes. The aim of this work is to characterize quantitatively the physical processes that are involved desorption kinetics CO-O2 ices by interpreting laboratory temperature programmed (TPD) data. This information used simulate behavior under astrophysical conditions. TPD spectra have recorded ultra high vacuum conditions pure, layered and mixed morphologies different thicknesses, temperatures...
Context. Circumstellar disks and envelopes of low-mass young stellar objects (YSOs) contain significant amounts ice. Such icy material will evolve to become volatile components planetary systems, such as comets in our solar system.
The low dust temperatures (<14 K) of Planck Galactic cold clumps (PGCCs) make them ideal targets to probe the initial conditions and very early phase star formation. "TOP-SCOPE" is a joint survey program targeting ∼2000 PGCCs in J = 1–0 transitions CO isotopologues ∼1000 850 μm continuum emission. objective surveys (SMT 10 m, KVN 21 NRO 45 m) statistically study occurring during formation evolution molecular clouds, across wide range environments. observations, data analysis, example science...
H2O is the most abundant component of astrophysical ices. In lines sight it not possible to fit both 3 um stretching, 6 bending and 13 libration band intensities with a single pure spectrum. Recent Spitzer observations have revealed CO2 ice in high abundances has been suggested that mixed into can affect relative strengths bands. We used laboratory infrared transmission spectroscopy H2O:CO2 mixtures investigate effects on spectral features at 15-135 K. find peak profiles are significantly...
Water in outflows from protostars originates either as a result of gas-phase synthesis atomic oxygen at T ≳ 200 K, or sputtered ice mantles containing water ice. We aim to quantify the contribution two mechanisms that lead outflows, by comparing observations methanol (a grain surface product) towards three low-mass NGC 1333. In doing so, we also amount destroyed outflows. To do this, make use James Clerk Maxwell Telescope and Herschel-Heterodyne Instrument for Far-Infrared data H2O, CH3OH CO...
The question of the nature water's glass transition has continued to be disputed over many years. Here we use slow heating scans (0.4 K min^{-1}) compact amorphous solid water deposited at 77 and an analysis accompanying changes in small-angle neutron scattering signal, study mesoscale ice network topology. From data infer onset rotational diffusion 115 K, a sudden switchover from nondiffusive motion enthalpy relaxation <121 diffusive across sample grains pore collapse >121 excellent...