1,827 research outputs found
Multipurpose High Frequency Electron Spin Resonance Spectrometer for Condensed Matter Research
We describe a quasi-optical multifrequency ESR spectrometer operating in the
75-225 GHz range and optimized at 210 GHz for general use in condensed matter
physics, chemistry and biology. The quasi-optical bridge detects the change of
mm wave polarization at the ESR. A controllable reference arm maintains a mm
wave bias at the detector. The attained sensitivity of 2x10^10 spin/G/(Hz)1/2,
measured on a dilute Mn:MgO sample in a non-resonant probe head at 222.4 GHz
and 300 K, is comparable to commercial high sensitive X band spectrometers. The
spectrometer has a Fabry-Perot resonator based probe head to measure aqueous
solutions, and a probe head to measure magnetic field angular dependence of
single crystals. The spectrometer is robust and easy to use and may be operated
by undergraduate students. Its performance is demonstrated by examples from
various fields of condensed matter physics.Comment: submitted to Journal of Magnetic Resonanc
Z-Spec: A MM-Wave Spectrometer For Measuring Redshifts Of Submillimeter Galaxies
We are building a background-limited, broadband millimeter-wave spectrometer (Z-Spec) for observations of CO rotational transitions from high-redshift dusty galaxies. The large instantaneous bandwidth (195 to 310 GHz) will enable redshifts of dust obscured galaxies to be unambiguously measured. Z-Spec uses a waveguide-coupled grating architecture in which the light propagation is confined within a parallel-plate waveguide. The grating is extremely compact compared to a classical free-space system. An array of silicon nitride bolometers cooled to 100 mK will provide background-limited performance. Z-Spec serves as a technology demonstration for a future space-borne far-infrared grating spectrometer
Homotopy types of stabilizers and orbits of Morse functions on surfaces
Let be a smooth compact surface, orientable or not, with boundary or
without it, either the real line or the circle , and
the group of diffeomorphisms of acting on by the rule
, where and .
Let be a Morse function and be the orbit of under this
action. We prove that for , and
except for few cases. In particular, is aspherical, provided so is .
Moreover, is an extension of a finitely generated free abelian
group with a (finite) subgroup of the group of automorphisms of the Reeb graph
of .
We also give a complete proof of the fact that the orbit is tame
Frechet submanifold of of finite codimension, and that the
projection is a principal locally trivial -fibration.Comment: 49 pages, 8 figures. This version includes the proof of the fact that
the orbits of a finite codimension of tame action of tame Lie group on tame
Frechet manifold is a tame Frechet manifold itsel
A Census of the High-Density Molecular Gas in M82
We present a three-pointing study of the molecular gas in the starburst
nucleus of M82 based on 190 - 307 GHz spectra obtained with Z-Spec at the
Caltech Submillimeter Observatory. We present intensity measurements,
detections and upper limits, for 20 transitions, including several new
detections of CS, HNC, C2H, H2CO, and CH3CCH lines. We combine our measurements
with previously-published measurements at other frequencies for HCN, HNC, CS,
C34S, and HCO+ in a multi-species likelihood analysis constraining gas mass,
density and temperature, and the species' relative abundances. We find some 1.7
- 2.7 x 10^8 M_sun of gas with n_H2 between 1 - 6 x 10^4 cm^-3 and T > 50 K.
While the mass and temperature are comparable to values inferred from mid-J CO
transitions, the thermal pressure is a factor of 10 - 20 greater. The molecular
interstellar medium is largely fragmented and is subject to ultraviolet
irradiation from the star clusters. It is also likely subject to cosmic rays
and mechanical energy input from the supernovae, and is warmer on average than
the molecular gas in the massive star formation regions in the Milky Way. The
typical conditions in the dense gas in M82's central kpc appear unfavorable for
further star formation; if any appreciable stellar populations are currently
forming, they are likely biased against low mass stars, producing a top-heavy
initial mass function.Comment: 15 pages (using emulateapj.cls), 6 figures, Astrophysical Journal, in
pres
The Warm Molecular Gas Around the Cloverleaf Quasar
We present the first broadband lambda = 1 mm spectrum toward the z=2.56
Cloverleaf Quasar, obtained with Z-Spec, a 1-mm grating spectrograph on the
10.4-meter Caltech Submillimeter Observatory. The 190-305 GHz observation band
corresponds to rest-frame 272 to 444 microns, and we measure the dust continuum
as well as all four transitions of carbon monoxide (CO) lying in this range.
The power-law dust emission, F_nu = 14 mJy (nu/240GHz)^3.9 is consistent with
the published continuum measurements. The CO J=6->5, J=8->7, and J=9->8
measurements are the first, and now provide the highest-J CO information in
this source. Our measured CO intensities are very close to the
previously-published interferometric measurements of J=7->6, and we use all
available transitions and our 13CO upper limits to constrain the physical
conditions in the Cloverleaf molecular gas disk. We find a large mass
(2-50x10^9 Msun) of highly-excited gas with thermal pressure nT > 10^6 Kcm^-3.
The ratio of the total CO cooling to the far-IR dust emission exceeds that in
the local dusty galaxies, and we investigate the potential heating sources for
this bulk of warm molecular gas. We conclude that both UV photons and X-rays
likely contribute, and discuss implications for a top-heavy stellar initial
mass function arising in the X-ray-irradiated starburst. Finally we present
tentative identifications of other species in the spectrum, including a
possible detection of the H20 2_0,2->1_1,1 transition at lambda_rest = 303
microns.Comment: ApJ in press, 12 pages in emulateAp
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