Energy Deposition and Photoelectric Emission from the Interaction of 10 eV to 1 MeV Photons with Interstellar Dust Particles

1996 ◽  
Vol 459 ◽  
pp. 686 ◽  
Author(s):  
Eli Dwek ◽  
Randall K. Smith
Keyword(s):  
Interstellar Dust ◽  
Energy Deposition ◽  
Dust Particles ◽  
Photoelectric Emission

scholarly journals Quantum tunneling observed without its characteristic large kinetic isotope effects

2015 ◽  
Vol 112 (24) ◽  
pp. 7438-7443 ◽  
Author(s):  
Tetsuya Hama ◽  
Hirokazu Ueta ◽  
Akira Kouchi ◽  
Naoki Watanabe
Keyword(s):  
Chemical Kinetics ◽  
Quantum Tunneling ◽  
Interstellar Dust ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
State Theory ◽  
Dust Particles ◽  
Interplanetary Dust Particles ◽  
Chemical Systems ◽  
Kinetic Isotope

Classical transition-state theory is fundamental to describing chemical kinetics; however, quantum tunneling is also important in explaining the unexpectedly large reaction efficiencies observed in many chemical systems. Tunneling is often indicated by anomalously large kinetic isotope effects (KIEs), because a particle’s ability to tunnel decreases significantly with its increasing mass. Here we experimentally demonstrate that cold hydrogen (H) and deuterium (D) atoms can add to solid benzene by tunneling; however, the observed H/D KIE was very small (1–1.5) despite the large intrinsic H/D KIE of tunneling (≳100). This strong reduction is due to the chemical kinetics being controlled not by tunneling but by the surface diffusion of the H/D atoms, a process not greatly affected by the isotope type. Because tunneling need not be accompanied by a large KIE in surface and interfacial chemical systems, it might be overlooked in other systems such as aerosols or enzymes. Our results suggest that surface tunneling reactions on interstellar dust may contribute to the deuteration of interstellar aromatic and aliphatic hydrocarbons, which could represent a major source of the deuterium enrichment observed in carbonaceous meteorites and interplanetary dust particles. These findings could improve our understanding of interstellar physicochemical processes, including those during the formation of the solar system.

scholarly journals Ortho and Parahydrogen in Interstellar Material

1979 ◽  
Vol 34 (2) ◽  
pp. 163-166 ◽  
Author(s):  
Robert R. Reeves ◽  
Paul Harteck
Keyword(s):  
Interstellar Dust ◽  
Dynamic Equilibrium ◽  
Exothermic Reaction ◽  
Statistical Weight ◽  
Dust Particles ◽  
Minor Role ◽  
Interstellar Space ◽  
Special Cases ◽  
Temperature Equilibrium ◽  
A Minor

Abstract Since H2 is the most abundant molecule in the universe, the ratio of orthohydrogen molecules to parahydrogen in interstellar space is of interest. H2, formed by any exothermic reaction will be in the ratio of 3: 1 according to their statistical weight. This corresponds to the high temperature equilibrium. At the low prevailing temperatures of interstellar space, the thermo-dynamic equilibrium should be shifted to the parahydrogen side. In the gas phase this shift can occur only over chemical reactions which are close to thermally neutral. In addition, it can be concluded that two ion scrambling reactions dominate the process and these both involve positive hydrogen ions. In special cases, surface catalysis on interstellar dust particles may add to the equilibrating process. The highly forbidden process of transition by radiation J = 1(ortho) → J = O(para) + hv can only play a minor role in this catalysis

scholarly journals Dust Measurements in the Outer Solar System

1994 ◽  
Vol 160 ◽  
pp. 367-380
Author(s):  
Eberhard Grün
Keyword(s):  
Solar System ◽  
Interstellar Dust ◽  
Thermal Emission ◽  
Scattered Light ◽  
Interplanetary Dust ◽  
Dust Particles ◽  
Spatial Density ◽  
Outer Solar System ◽  
The Sun

In-situ measurements of micrometeoroids provide information on the spatial distribution of interplanetary dust and its dynamical properties. Pioneers 10 and 11, Galileo and Ulysses spaceprobes took measurements of interplanetary dust from 0.7 to 18 AU distance from the sun. Distinctly different populations of dust particles exist in the inner and outer solar system. In the inner solar system, out to about 3 AU, zodiacal dust particles are recognized by their scattered light, their thermal emission and by in-situ detection from spaceprobes. These particles orbit the sun on low inclination (i ≤ 30°) and moderate eccentricity (e ≤ 0.6) orbits. Their spatial density falls off with approximately the inverse of the solar distance. Dust particles on high inclination or even retrograde trajectories dominate the dust population outside about 3 AU. The dust detector on board the Ulysses spaceprobe identified interstellar dust sweeping through the outer solar system on hyperbolic trajectories. Within about 2 AU from Jupiter Ulysses discovered periodic streams of dust particles originating from within the jovian system.

scholarly journals Penetration of Interstellar Dust Aggregates Into Circumstellar Dust Disks

2004 ◽  
Vol 202 ◽  
pp. 347-349
Author(s):  
Hiroshi Kimura ◽  
Ingrid Mann
Keyword(s):  
Interstellar Medium ◽  
Physical Properties ◽  
Relative Motion ◽  
Interstellar Dust ◽  
Dust Particles ◽  
Circumstellar Dust ◽  
Circumstellar Disk ◽  
Dust Disks

Interstellar dust particles, which are supposedly aggregates, penetrate dust disks around stars because of the star's motion relative to the surrounding interstellar medium (ISM). We discuss the interrelation of the physical properties of local interstellar dust, the relative motion of the star and the surrounding ISM, and the evolution of the circumstellar disk.

scholarly journals Interstellar Dust and the H2 Molecule

1965 ◽  
Vol 7 ◽  
pp. 259-264
Author(s):  
K. H. Schmidt
Keyword(s):  
Hydrogen Atom ◽  
Molecular Hydrogen ◽  
Interstellar Dust ◽  
Unit Volume ◽  
Formation Rate ◽  
Dust Particles ◽  
Interstellar Gas ◽  
The Past ◽  
Grain Surface ◽  
H2 Molecule

Nearly 20 Years Ago van de Hulst stated that the formation of molecular hydrogen occurs on the surfaces of the interstellar grains. (See ref. 1.) In the last years several authors discussed the problem of the interstellar abundance of the H2 molecule. (See refs. 2 to 9.) They all found that the percentage of the molecular hydrogen in the interstellar gas probably is much larger than had been thought in the past and that the essential mechanism of H2 formation is the formation on the particle surfaces. Therefore, the formation rate of interstellar H2 is a function of the area of the grain surface per unit volume, which is dependent on the average radius of the grains ā, on the number of dust particles per unit volume N(ā), and on the distribution function of the particle radii. The formation rate is determined by the density of the atomic hydrogen nH and the temperature of the interstellar gas Tgas. Finally, the formation rate of H2 depends on the probability π that an impinging hydrogen atom on a grain joins with another hydrogen atom to form a molecule.

Destiny+ Dust Analyzer – Campaign & timeline preparation for interplanetary & interstellar dust observation during the 4-year transfer phase from Earth to Phaethon

2020 ◽  
Author(s):  
Maximilian Sommer ◽  
Harald Krüger ◽  
Ralf Srama ◽  
Takayuki Hirai ◽  
Masanori Kobayashi ◽  
...  
Keyword(s):  
Electric Propulsion ◽  
Interstellar Dust ◽  
Impact Ionization ◽  
Interplanetary Space ◽  
Dust Cloud ◽  
Dust Particles ◽  
Transfer Phase ◽  
Moon System ◽  
The Earth ◽  
The Impact

<p align="justify">The Destiny+ mission (Demonstration and Experiment of Space Technology for Interplanetary voyage Phaethon fLyby and dUst Science) has been selected as part of its M-class Space Science Program by the Japanese space agency JAXA/ISAS and is set to launch in 2023/2024. The mission target is the active asteroid (3200) Phaethon with a projected flyby in early 2028. The scientific payload consists of two cameras (the Telescopic Camera for Phaethon, TCAP, and the Multi-band Camera for Phaethon, MCAP), and the Destiny+ Dust Analyzer (DDA). DDA is the technological successor to the Cosmic Dust Analyzer (CDA) aboard Cassini-Huygens, which prominently investigated the dust environment of the Saturnian system. The DDA sensor is designed as a combination of impact ionization time-of-flight mass spectrometer and trajectory sensor, which will allow for the analysis of sub-micron and micron sized dust particles with respect to their composition (mass resolution m/Δm ≈ 100-150), mass, electrical charge, velocity (about 10% accuracy), and impact direction (about 10° accuracy).</p> <p align="justify">Besides attempting to sample the impact-generated dust cloud around Phaethon during the flyby, DDA will be actively observing the interplanetary & interstellar dust environment over the roughly four years spanning cruise phase from the Earth-Moon system through interplanetary space. After launch into a GTO-like orbit, Destiny+ will first employ its solar-electric propulsion system to spiral up to the lunar orbit within about 18 months, followed by a series of lunar swingbys and interim coasting phases in distant cislunar space, accumulating momentum to leave the Earth-Moon system at high excess velocity. The subsequent roughly 2-year interplanetary transfer to intercept Phaethon will be characterized by moderate orbital eccentricity of up to 0.1 and largely unpowered coasting phases.</p> <p align="justify">During these four years, the DDA sensor will benefit from a maximum pointing coverage range enabled by its dual-axis pointing mechanism and spacecraft attitude flexibility (during times of unpowered flight). This will allow for exhaustive mapping and analysis of the different interplanetary dust populations, as well as interstellar dust encountered in the region between 0.9-1.1 AU.</p> <p align="justify">Here, we give a progress report on the science planning efforts for the 4-year transfer phase. We present a tentative observation timeline that assigns scientific campaigns to different phases of the mission, taking into account results of various dust models, as well as operational and technical constraints.</p>

ERE from Graphene Oxide in the ISM. A possible link to IOM?

2020 ◽  
Author(s):  
Peter Sarre
Keyword(s):  
Graphene Oxide ◽  
Organic Material ◽  
Interstellar Dust ◽  
Emission Spectra ◽  
Optical Emission ◽  
Interplanetary Dust ◽  
Infrared Emission ◽  
Dust Particles ◽  
Interplanetary Dust Particles ◽  
Infrared Space Observatory

<p>Dust particles play a major role in the formation, evolution and chemistry of interstellar clouds, stars, and planetary systems. Commonly identified forms include amorphous and crystalline carbon-rich particles and silicates. Also present in many astrophysical environments are polycyclic aromatic hydrocarbons (PAHs), detected through their infrared emission, and which are essentially small flakes of graphene. Astronomical observations over the past four decades have revealed a widespread unassigned ‘extended red emission’ (ERE) feature which is attributed to luminescence of dust grains. A luminescence feature with similar characteristics to ERE has been found in organic material in interplanetary dust particles and carbonaceous chondrites.  </p> <p>There is a strong similarity between laboratory optical emission spectra of graphene oxide (GO) and ERE, leading to this proposal that emission from GO nanoparticles is the origin of ERE and that heteroatom-containing PAH structures are a significant component of interstellar dust. The proposal is supported by infrared emission features detected by the <em>Infrared Space Observatory (ISO)</em> and the <em>Spitzer Space Telescope</em>.  </p> <p>Insoluble Organic Material (IOM) has a chemical structure with some similarities to graphene oxide.  It is suggested this may contribute to the discussion as to whether IOM has an origin in the interstellar medium or the solar nebula, or some combination.</p>

Prebiotic synthesis of bioorganic compounds in simulated interstellar dust particles

1996 ◽  
Vol 26 (3-5) ◽  
pp. 321-322 ◽  
Author(s):  
Takashi Kasamatsu ◽  
Takeo Kaneko ◽  
Kensei Kobayashi ◽  
Akira Kouchi ◽  
Takeshi Saito
Keyword(s):  
Interstellar Dust ◽  
Prebiotic Synthesis ◽  
Dust Particles ◽  
Bioorganic Compounds
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