80 research outputs found
Miniature cyclotron resonance ion source using small permanent magnet
An ion source using the cyclotron resonance principle is described. A miniaturized ion source device is used in an air gap of a small permanent magnet with a substantially uniform field in the air gap of about 0.5 inch. The device and permanent magnet are placed in an enclosure which is maintained at a high vacuum (typically 10 to the minus 7th power) into which a sample gas can be introduced. The ion beam end of the device is placed very close to an aperture through which an ion beam can exit into the apparatus for an experiment
Quantification of UV stimulated ice chemistry: CO and CO2
Recent laboratory experiments are presented that show that during photolysis of the pure ices there is evidence of the interconversion of CO to CO2 and CO2 to CO using Lyman alpha (1216A) radiation. In addition, there is a substantial amount of another substance being produced. This substance is evident by its infrared absorption peak at 2235 cm(-1). It is believed that this new peak is due to carbon suboxide, C3O2. CO and CO2 have already been detected in comets, and C3O2 has been suggested as a cometary from radiation of CO. Comparisons are made between our results at 1215A and proton radiation experiments and radiation at other wavelengths. The suggestion is that the processing of ices is energy dependent, i.e., dependent on the type of radiation. Several difficult problems have to be solved before these radiation conversions can be quantified. The steps that we are taking to quantify the kinetics are discussed
Getting a Grip on the Transverse Motion in a Zeeman Decelerator
Zeeman deceleration is an experimental technique in which inhomogeneous,
time-dependent magnetic fields generated inside an array of solenoid coils are
used to manipulate the velocity of a supersonic beam. A 12-stage Zeeman
decelerator has been built and characterized using hydrogen atoms as a test
system. The instrument has several original features including the possibility
to replace each deceleration coil individually. In this article, we give a
detailed description of the experimental setup, and illustrate its performance.
We demonstrate that the overall acceptance in a Zeeman decelerator can be
significantly increased with only minor changes to the setup itself. This is
achieved by applying a rather low, anti-parallel magnetic field in one of the
solenoid coils that forms a temporally varying quadrupole field, and improves
particle confinement in the transverse direction. The results are reproduced by
three-dimensional numerical particle trajectory simulations thus allowing for a
rigorous analysis of the experimental data. The findings suggest the use of a
modified coil configuration to improve transverse focusing during the
deceleration process.Comment: accepted by J. Chem. Phy
An ICR study of ion-molecules reactions relevant to titan’s atmosphere: An investigation of binary hydrocarbon mixtures up to 1 Micron
Termolecular ion-molecule reactions in Titan’s atmosphere. IV. A search made at up to 1 micron in pure hydrocarbons
Chemistry of chlorine in dense interstellar clouds
Laboratory experiments and theoretical modeling show that the chemistry of chlorine is fairly simple in dense interstellar clouds, with Cl and HCl as the only species whose fractional abundances are significant. The estimated fraction of gas-phase chlorine present as HCl lies between 25-65 percent, in good agreement with the recent observations of the ground state HCl transition by Blake, Keene, and Philips (1985). These results, combined with the observational limits on HCl, indicate that chlorine is not severely depleted in dense interstellar clouds
Composition of Titan's ionosphere
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94758/1/grl21212.pd
Using high resolution and dynamic reaction cell for the improvement of the sensitivity of direct silicon determination in uranium materials by inductively coupled plasma mass spectrometry
Chemistry in disks I - Deep search for NH in the protoplanetary disks around LkCa 15, MWC 480, and DM Tau
Aims: To constrain the ionization fraction in protoplanetary disks, we
present new high-sensitivity interferometric observations of NH in
three disks surrounding DM Tau, LkCa 15, and MWC 480. Methods: We used the IRAM
PdBI array to observe the NH J=1-0 line and applied a
-minimization technique to estimate corresponding column densities.
These values are compared, together with HCO column densities, to results
of a steady-state disk model with a vertical temperature gradient coupled to
gas-grain chemistry. Results: We report two \ndhp detections for LkCa 15 and DM
Tau at the level and an upper limit for MWC 480. The column density
derived from the data for LkCa 15 is much lower than previously reported. The
[NH/HCO] ratio is on the order of 0.02--0.03. So far, HCO
remains the most abundant observed molecular ion in disks. Conclusions: All the
observed values generally agree with the modelled column densities of disks at
an evolutionary stage of a few million years (within the uncertainty limits),
but the radial distribution of the molecules is not reproduced well. The low
inferred concentration of NH in three disks around low-mass and
intermediate-mass young stars implies that this ion is not a sensitive tracer
of the overall disk ionization fraction.Comment: 10 pages, 6 figure
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