258 research outputs found
A time-resolution study with a plastic scintillator read out by a Geiger-mode Avalanche Photodiode
In this work we attempt to establish the best time resolution attainable with
a scintillation counter consisting of a plastic scintillator read out by a
Geiger-mode Avalanche Photodiode. The measured time resolution is inversely
proportional to the square root of the energy deposited in the scintillator,
and scales to 18ps (sigma) at 1MeV. This result competes with the best ones
reported for photomultiplier tubes.Comment: 8 pages, 8 figure
Long-range interactions between an atom in its ground S state and an open-shell linear molecule
Theory of long-range interactions between an atom in its ground S state and a
linear molecule in a degenerate state with a non-zero projection of the
electronic orbital angular momentum is presented. It is shown how the
long-range coefficients can be related to the first and second-order molecular
properties. The expressions for the long-range coefficients are written in
terms of all components of the static and dynamic multipole polarizability
tensor, including the nonadiagonal terms connecting states with the opposite
projection of the electronic orbital angular momentum. It is also shown that
for the interactions of molecules in excited states that are connected to the
ground state by multipolar transition moments additional terms in the
long-range induction energy appear. All these theoretical developments are
illustrated with the numerical results for systems of interest for the
sympathetic cooling experiments: interactions of the ground state Rb(S)
atom with CO(), OH(), NH(), and CH() and of the
ground state Li(S) atom with CH().Comment: 30 pages, 3 figure
Precise study of asymptotic physics with subradiant ultracold molecules
Weakly bound molecules have physical properties without atomic analogues,
even as the bond length approaches dissociation. In particular, the internal
symmetries of homonuclear diatomic molecules result in formation of two-body
superradiant and subradiant excited states. While superradiance has been
demonstrated in a variety of systems, subradiance is more elusive due to the
inherently weak interaction with the environment. Here we characterize the
properties of deeply subradiant molecular states with intrinsic quality factors
exceeding via precise optical spectroscopy with the longest
molecule-light coherent interaction times to date. We find that two competing
effects limit the lifetimes of the subradiant molecules, with different
asymptotic behaviors. The first is radiative decay via weak magnetic-dipole and
electric-quadrupole interactions. We prove that its rate increases
quadratically with the bond length, confirming quantum mechanical predictions.
The second is nonradiative decay through weak gyroscopic predissociation, with
a rate proportional to the vibrational mode spacing and sensitive to
short-range physics. This work bridges the gap between atomic and molecular
metrology based on lattice-clock techniques, yielding new understanding of
long-range interatomic interactions and placing ultracold molecules at the
forefront of precision measurements.Comment: 12 pages, 6 figure
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