516 research outputs found
On deflection fields, weak-focusing and strong-focusing storage rings for polar molecules
In this paper, we analyze electric deflection fields for polar molecules in
terms of a multipole expansion and derive a simple but rather insightful
expression for the force on the molecules. Ideally, a deflection field exerts a
strong, constant force in one direction, while the force in the other
directions is zero. We show how, by a proper choice of the expansion
coefficients, this ideal can be best approximated. We present a design for a
practical electrode geometry based on this analysis. By bending such a
deflection field into a circle, a simple storage ring can be created; the
direct analog of a weak-focusing cyclotron for charged particles. We show that
for realistic parameters a weak-focusing ring is only stable for molecules with
a very low velocity. A strong-focusing (alternating-gradient) storage ring can
be created by arranging many straight deflection fields in a circle and by
alternating the sign of the hexapole term between adjacent deflection fields.
The acceptance of this ring is numerically calculated for realistic parameters.
Such a storage might prove useful in experiments looking for an EDM of
elementary particles.Comment: 8 pages, 5 figure
Sensitivity of rotational transitions in CH and CD to a possible variation of fundamental constants
The sensitivity of rotational transitions in CH and CD to a possible
variation of fundamental constants has been investigated. Largely enhanced
sensitivity coefficients are found for specific transitions which are due to
accidental degeneracies between the different fine-structure manifolds. These
degeneracies occur when the spin-orbit coupling constant is close to four times
the rotational constant. CH and particularly CD match this condition closely.
Unfortunately, an analysis of the transition strengths shows that the same
condition that leads to an enhanced sensitivity suppresses the transition
strength, making these transitions too weak to be of relevance for testing the
variation of fundamental constants over cosmological time scales. We propose a
test in CH based on the comparison between the rotational transitions between
the e and f components of the Omega'=1/2,J=1/2 and Omega'=3/2,J=3/2 levels at
532 and 536 GHz and other rotational or Lambda-doublet transitions in CH
involving the same absorbing ground levels. Such a test, to be performed by
radioastronomy of highly redshifted objects, is robust against systematic
effects
Ramsey-type microwave spectroscopy on CO ()
Using a Ramsey-type setup, the lambda-doublet transition in the level of the state of CO was measured to be 394 064 870(10)
Hz. In our molecular beam apparatus, a beam of metastable CO is prepared in a
single quantum level by expanding CO into vacuum and exciting the molecules
using a narrow-band UV laser system. After passing two microwave zones that are
separated by 50 cm, the molecules are state-selectively deflected and detected
1 meter downstream on a position sensitive detector. In order to keep the
molecules in a single level, a magnetic bias field is applied. We find
the field-free transition frequency by taking the average of the and transitions,
which have an almost equal but opposite Zeeman shift. The accuracy of this
proof-of-principle experiment is a factor of 100 more accurate than the
previous best value obtained for this transition
Species richness and susceptibility to heat and drought extremes in synthesized grassland ecosystems: compositional vs physiological effects
UV frequency metrology on CO (a3Pi); isotope effects and sensitivity to a variation of the proton-to-electron mass ratio
UV frequency metrology has been performed on the a3Pi - X1Sigma+ (0,0) band
of various isotopologues of CO using a frequency-quadrupled injection-seeded
narrow-band pulsed Titanium:Sapphire laser referenced to a frequency comb
laser. The band origin is determined with an accuracy of 5 MHz (delta \nu / \nu
= 3 * 10^-9), while the energy differences between rotational levels in the
a3Pi state are determined with an accuracy of 500 kHz. From these measurements,
in combination with previously published radiofrequency and microwave data, a
new set of molecular constants is obtained that describes the level structure
of the a3Pi state of 12C16O and 13C16O with improved accuracy. Transitions in
the different isotopologues are well reproduced by scaling the molecular
constants of 12C16O via the common mass-scaling rules. Only the value of the
band origin could not be scaled, indicative of a breakdown of the
Born-Oppenheimer approximation. Our analysis confirms the extreme sensitivity
of two-photon microwave transitions between nearly-degenerate rotational levels
of different Omega-manifolds for probing a possible variation of the
proton-to-electron mass ratio, \mu=m_p/m_e, on a laboratory time scale
The effect and process evaluations of the national quality improvement programme for palliative care : the study protocol
Background: The nationwide integration of palliative care best practices into general care settings is challenging but important in improving the quality of palliative care. This is why the Dutch National Quality Improvement Programme for Palliative Care has recently been launched. This four-year programme consists of about 70 implementation trajectories of best practices. A large evaluation study has been set up to evaluate this national programme and separate implementation trajectories.
Methods/Design: This paper presents the protocol of the evaluation study consisting of a quantitative effect evaluation and a qualitative process evaluation. The effect evaluation has a pre-test post-test design, with measurements before implementation (month 0) and after implementation (month 9) of a best practice. Patients are eligible if they have a life expectancy of less than six months and/or if they are undergoing palliative treatment and provided they are physically and mentally capable of responding to questionnaires. Bereaved relatives are eligible if they have been involved in the care of a deceased patient who died after a sickbed between six weeks and six months ago. Three types of measurement instruments are used: (1) numerical rating scales for six symptoms (pain, fatigue, breathlessness, obstipation, sadness and anxiety), (2) the Consumer Quality Index Palliative Care - patient version and (3) the version for bereaved relatives. The process evaluation consists of analysing implementation plans and reports of the implementation, and individual and group interviews with healthcare professionals. This will be done nine to eleven months after the start of the implementation of a best practice.
Discussion: This mixed-method evaluation study gives more insight into the effects of the total programme and the separate implementation trajectories. However, evaluation of large quality improvement programmes is complicated due to changing, non-controlled environments. Therefore, it is important that an effect evaluation is combined with a process evaluation
Vicinal Surfaces and the Calogero-Sutherland Model
A miscut (vicinal) crystal surface can be regarded as an array of meandering
but non-crossing steps. Interactions between the steps are shown to induce a
faceting transition of the surface between a homogeneous Luttinger liquid state
and a low-temperature regime consisting of local step clusters in coexistence
with ideal facets. This morphological transition is governed by a hitherto
neglected critical line of the well-known Calogero-Sutherland model. Its exact
solution yields expressions for measurable quantities that compare favorably
with recent experiments on Si surfaces.Comment: 4 pages, revtex, 2 figures (.eps
Increased Turnover but Little Change in the Carbon Balance of High-Arctic Tundra Exposed to Whole Growing Season Warming
Pulsed Molecular Optomechanics in Plasmonic Nanocavities: From Nonlinear Vibrational Instabilities to Bond-Breaking
Small numbers of surface-bound molecules are shown to behave as would be expected for opto-mechanical oscillators placed inside plasmonic nano-cavities that support extreme confinement of optical fields. Pulsed Raman scattering reveals superlinear Stokes emission above a threshold, arising from the stimulated vibrational pumping of molecular bonds under pulsed excitation shorter than the phonon decay time, and agreeing with pulsed optomechanical quantum theory. Reaching the parametric instability (equivalent to a phonon laser or ‘phaser’ regime) is however hindered by motion of gold atoms and molecular reconfiguration at phonon occupations approaching unity. We show how this irreversible bond breaking can ultimately limit the exploitation of molecules as quantum mechanical oscillators, but accesses optically-driven chemistry
Correlation decay and conformal anomaly in the two-dimensional random-bond Ising ferromagnet
The two-dimensional random-bond Ising model is numerically studied on long
strips by transfer-matrix methods. It is shown that the rate of decay of
correlations at criticality, as derived from averages of the two largest
Lyapunov exponents plus conformal invariance arguments, differs from that
obtained through direct evaluation of correlation functions. The latter is
found to be, within error bars, the same as in pure systems. Our results
confirm field-theoretical predictions. The conformal anomaly is calculated
from the leading finite-width correction to the averaged free energy on strips.
Estimates thus obtained are consistent with , the same as for the pure
Ising model.Comment: RevTeX 3, 11 pages +2 figures, uuencoded, IF/UFF preprin
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