3,634 research outputs found
Observation of b symmetry vibrational levels of the SO \tilde{\mbox{C}} B state: Vibrational level staggering, Coriolis interactions, and rotation-vibration constants
The B state of SO has a double-minimum
potential in the antisymmetric stretch coordinate, such that the minimum energy
geometry has nonequivalent SO bond lengths. However, low-lying levels with odd
quanta of antisymmetric stretch (b vibrational symmetry) have not
previously been observed because transitions into these levels from the
zero-point level of the state are vibronically forbidden.
We use IR-UV double resonance to observe the b vibrational levels of the
state below 1600 cm of vibrational excitation. This
enables a direct characterization of the vibrational level staggering that
results from the double-minimum potential. In addition, it allows us to
deperturb the strong -axis Coriolis interactions between levels of a and
b vibrational symmetry, and to determine accurately the vibrational
dependence of the rotational constants in the distorted
electronic state
Visible and Ultraviolet Laser Spectroscopy of ThF
The molecular ion ThF is the species to be used in the next generation of
search for the electron's Electric Dipole Moment (eEDM) at JILA. The
measurement requires creating molecular ions in the eEDM sensitive state, the
rovibronic ground state , , . Survey spectroscopy of
neutral ThF is required to identify an appropriate intermediate state for a
Resonance Enhanced Multi-Photon Ionization (REMPI) scheme that will create ions
in the required state. We perform broadband survey spectroscopy (from 13000 to
44000~cm) of ThF using both Laser Induced Fluorescence (LIF) and
REMPI spectroscopy. We observe and assign 345 previously unreported vibronic
bands of ThF. We demonstrate 30\% efficiency in the production of ThF ions
in the eEDM sensitive state using the [32.85] intermediate
state. In addition, we propose a method to increase the aforementioned
efficiency to 100\% by using vibrational autoionization via
core-nonpenetrating Rydberg states, and discuss theoretical and experimental
challenges. Finally, we also report 83 vibronic bands of an impurity species,
ThO.Comment: 49 pages, 7 figure
Collisional depolarization of state selected (J,M J ) BaO Aâ1ÎŁ+ measured by opticalâoptical double resonance
The opticalâoptical double resonance (OODR) technique is used to investigate the change in magnetic quantum number (M) a state selected molecule undergoes on collision with other molecules. A first linearly polarized dye laser prepares Aâ 1ÎŁ+BaO(v = 1) in the J = 1, M = 0 sublevel. The extent of collisional transfer to other M sublevels of both J = 1 and J = 2 is then probed by a second polarized dye laser which induces fluorescence from the Câ 1ÎŁ+ state. Elastic collisions (ÎJ = 0) between BaO (Aâ 1ÎŁ+) and CO2 are observed to change M from 0 to ±1 leaving J unchanged. The total elasticMâchanging cross section is ÏÎM CO2 = 8.4±2.4 Ă
2. Inelastic collisions (ÎJ = +1â which transfer molecules to j = 2 also cause M changes. with both Ar and CO2 as collision partners. M, the s p a c eâf i x e d projection of J, is found to be neither conserved nor randomized. Quantum atomâdiatom collision models with quantization axis along the relative velocity vector are considered. Transition amplitudes in this system are evaluated using the lâdominant and CS approximations
CuAAC click chemistry for the enhanced detection of novel alkyne-based natural product toxins
In the context of discovering and quantifying terminal alkyne-based natural products, here we report the combination of CuAAC click chemistry with LC-MS for the detection of polyether toxins (prymnesins) associated with harmful algal blooms. The added-value of the CuAAC-based approach is evident from our ability to detect novel prymnesin-like compounds in algal species with previously uncharacterised toxins
Laser-induced fluorescence studies of HfF+ produced by autoionization
Autoionization of Rydberg states of HfF, prepared using the optical-optical
double resonance (OODR) technique, holds promise to create HfF+ in a particular
Zeeman level of a rovibronic state for an electron electric dipole moment
(eEDM) search. We characterize a vibronic band of Rydberg HfF at 54 cm-1 above
the lowest ionization threshold and directly probe the state of the ions formed
from this vibronic band by performing laser-induced fluorescence (LIF) on the
ions. The Rydberg HfF molecules show a propensity to decay into only a few ion
rotational states of a given parity and are found to preserve their orientation
qualitatively upon autoionization. We show empirically that we can create 30%
of the total ion yield in a particular |J+,M+> state and present a simplified
model describing autoionization from a given Rydberg state that assumes no
angular dynamics.Comment: 8 pages, 5 figure
Molecular Orientation by Intense Single Cycle THz Pulses
Intense single-cycle THz pulses resonantly interacting with molecular
rotations are shown to induce significant field-free orientation under ambient
conditions. We calculate and measure the angular distribution associated with
THz-driven rotational motion and correlate the THz-induced orientation and
alignment in an OCS gas sample.Comment: 8 pages, 3 figures, presented at OTST 2011, presented at FRISNO 11
PDF available on FRISNO 11 website -
http://www.weizmann.ac.il/conferences/frisno11/uploads/Fleischer_Zhou_Field_Nelson_frisno11_PDF.pd
Restructuring the Tridiagonal and Bidiagonal QR Algorithms for Performance
We show how both the tridiagonal and bidiagonal QR algorithms can be restructured so that they be-
come rich in operations that can achieve near-peak performance on a modern processor. The key is a
novel, cache-friendly algorithm for applying multiple sets of Givens rotations to the eigenvector/singular
vector matrix. This algorithm is then implemented with optimizations that (1) leverage vector instruction
units to increase floating-point throughput, and (2) fuse multiple rotations to decrease the total number of
memory operations. We demonstrate the merits of these new QR algorithms for computing the Hermitian
eigenvalue decomposition (EVD) and singular value decomposition (SVD) of dense matrices when all eigen-
vectors/singular vectors are computed. The approach yields vastly improved performance relative to the
traditional QR algorithms for these problems and is competitive with two commonly used alternativesâ
Cuppenâs Divide and Conquer algorithm and the Method of Multiple Relatively Robust Representationsâ
while inheriting the more modest O(n) workspace requirements of the original QR algorithms. Since the
computations performed by the restructured algorithms remain essentially identical to those performed by
the original methods, robust numerical properties are preserved
Prediction of signalâtoânoise ratio gain for passive higherâorder correlation detection of energy transients
In general, higherâorder correlation detectors perform well in passive detection for signals of high thirdâ and fourthâorder moments. Previous studies by the authors have shown that the normalized thirdâ and fourthâorder signal moments are reliable indicators of higherâorder correlation detector performance [Pflug et al. (1992b)]. For a deterministic energy transient of known moments through fourth order, it is possible to predict theoretically the amount of gain over an ordinary crossâcorrelation detector for a bicorrelation or tricorrelation detector applied in a noise environment of known variance. In this paper, formulas that predict detector performance for passive detection at the minimum detectable level are derived. The noise is assumed to be stationary and zero mean with Gaussian correlation central ordinate probability density functions. To test the formulas, SNR detection and gain curves are generated using hypothesis testing and Monte Carlo simulations on a set of test signals. The test signals are created by varying the time width of a pulseâlike signal in a sampling window of fixed time duration, resulting in a set of test signals with varying signal moments. Good agreement is found between the simulated and theoretical results. The effects of observation time (length of detection window) and sampling interval on detector performance are also discussed and illustrated with computer simulations. The prediction formulas indicate that decreasing the observation time or the sampling interval (assuming the signal is sufficiently sampled and the detection window contains the entire signal) improves detection performance. However, the rate of improvement is different for the three detectors. The SNR required to achieve the minimum detectable level of detection performance at a given probability of false alarm (Pfa) decreases with the fourth root of the observation time and sampling interval for the crossâcorrelation detector, the sixth root for the bicorrelation detector, and the eighth root for the tricorrelation detector. Relative detector performance also varies with Pfa. The probability of detection (Pd) for higherâorder detectors degrades less rapidly with decreasing Pfa than the Pd for ordinary correlations. Thus higherâorder correlators can be especially appropriate when a very low Pfa is required
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