30,908 research outputs found
OH hyperfine ground state: from precision measurement to molecular qubits
We perform precision microwave spectroscopy--aided by Stark deceleration--to
reveal the low magnetic field behavior of OH in its ^2\Pi_{3/2} ro-vibronic
ground state, identifying two field-insensitive hyperfine transitions suitable
as qubits and determining a differential Lande g-factor of
1.267(5)\times10^{-3} between opposite parity components of the
\Lambda-doublet. The data are successfully modeled with an effective hyperfine
Zeeman Hamiltonian, which we use to make a tenfold improvement of the
magnetically sensitive, astrophysically important \Delta F=\pm1 satellite-line
frequencies, yielding 1720529887(10) Hz and 1612230825(15) Hz.Comment: 4+ pages, 3 figure
The Deformation of an Elastic Substrate by a Three-Phase Contact Line
Young's classic analysis of the equilibrium of a three-phase contact line
ignores the out-of-plane component of the liquid-vapor surface tension. While
it has long been appreciated that this unresolved force must be balanced by
elastic deformation of the solid substrate, a definitive analysis has remained
elusive because conventional idealizations of the substrate imply a divergence
of stress at the contact line. While a number of theories of have been
presented to cut off the divergence, none of them have provided reasonable
agreement with experimental data. We measure surface and bulk deformation of a
thin elastic film near a three-phase contact line using fluorescence confocal
microscopy. The out-of-plane deformation is well fit by a linear elastic theory
incorporating an out-of-plane restoring force due to the surface tension of the
gel. This theory predicts that the deformation profile near the contact line is
scale-free and independent of the substrate elastic modulus.Comment: 4 pages, 3 figure
Giant microwave photoresistance of two-dimensional electron gas
We measure microwave frequency (4-40 GHz) photoresistance at low magnetic
field B, in high mobility 2D electron gas samples, excited by signals applied
to a transmission line fabricated on the sample surface. Oscillatory
photoresistance vs B is observed. For excitation at the cyclotron resonance
frequency, we find an unprecedented, giant relative photoresistance (\Delta
R)/R of up to 250 percent. The photoresistance is apparently proportional to
the square root of applied power, and disappears as the temperature is
increased.Comment: 4 pages, 3 figure
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