Atomic And Molecular Clusters
User Manual for MOLSCAT, BOUND and FIELD: programs for quantum scattering properties and bound states of interacting pairs of atoms and molecules (1903.06755v1)
Jeremy M. Hutson, C. Ruth Le Sueur
2019-03-15
MOLSCAT is a general-purpose package for performing non-reactive quantum scattering calculations for atomic and molecular collisions using coupled-channel methods. Simple atom-molecule and molecule-molecule collision types are coded internally and additional ones may be handled with plug-in routines. Plug-in routines may include external magnetic, electric or photon fields (and combinations of them). Simple interaction potentials are coded internally and more complicated ones may be handled with plug-in routines. BOUND is a general-purpose package for performing calculations of bound-state energies in weakly bound atomic and molecular systems using coupled-channel methods. It solves the same sets of coupled equations as \MOLSCAT, and can use the same plug-in routines if desired, but with different boundary conditions. FIELD is a development of BOUND that locates external fields at which a bound state exists with a specified energy. One important use is to locate the positions of magnetically tunable Feshbach resonance positions in ultracold collisions. Previous versions of these programs have been released separately. However, there is a significant degree of overlap between their internal structures and usage specifications. This manual therefore describes all three, with careful identification of parts that are specific to one or two of the programs.
Spectra of the D2O dimer in the O-D fundamental stretch region: vibrational dependence of tunneling splittings and lifetimes (1903.06596v1)
A. J. Barclay, A. R. W. McKellar, N. Moazzen-Ahmadi
2019-03-15
The fundamental O-D stretch region (2600 - 2800 cm-1) of the fully deuterated water dimer, (D2O)2, is studied using a pulsed supersonic slit jet source and a tunable optical parametric oscillator source. Relatively high spectral resolution (0.002 cm-1) enables all six dimer tunneling components to be observed, in most cases, for the acceptor asymmetric O-D stretch, the donor free O-D stretch, and the donor bound O-D stretch vibrations. The dominant acceptor switching tunneling splittings are observed to decrease moderately in the excited O-D stretch states, to roughly 75% of their ground state values, whereas the smaller donor-acceptor interchange splittings show more dramatic and irregular decreases. Excited state predissociation lifetimes, as determined from observed line broadening, show large variations (0.2 to 5 nanoseconds) depending on vibrational state, K-value, and tunneling symmetry. Another very weak band is tentatively assigned to a combination mode involving an intramolecular O-D stretch plus an intermolecular twist overtone. Asymmetric O-D stretch bands of the mixed isotopologue dimers D2O-DOH and D2O-HOD are also observed and analyzed.
BOUND and FIELD: programs for calculating bound states of interacting pairs of atoms and molecules (1811.09111v2)
Jeremy M. Hutson, C. Ruth Le Sueur
2018-11-22
The BOUND program calculates the bound states of a complex formed from two interacting particles using coupled-channel methods. It is particularly suitable for the bound states of atom-molecule and molecule-molecule Van der Waals complexes and for the near-threshold bound states that are important in ultracold physics. It uses a basis set for all degrees of freedom except
, the separation of the centres of mass of the two particles. The Schr"odinger equation is expressed as a set of coupled equations in
Rotational spectroscopy as a tool to investigate interactions between vibrational polyads in symmetric top molecules: low-lying states 
of methyl cyanide, CH
CN (1502.06867v2)
Holger S. P. Müller, Linda R. Brown, Brian J. Drouin, John C. Pearson, Isabelle Kleiner, Robert L. Sams, Keeyoon Sung, Matthias H. Ordu, Frank Lewen
2015-02-24
Spectra of methyl cyanide were recorded to analyze interactions in low-lying vibrational states and to construct line lists for radio astronomical observations as well as for infrared spectroscopic investigations of planetary atmospheres. The rotational spectra cover large portions of the 36
1627 GHz region. In the infrared (IR), a spectrum was recorded for this study in the region of 2
around 717 cm
with assignments covering 684
and
quantum numbers and allowed us to investigate for the first time in depth local interactions between these states which occur at high
and 2. Notably, there is a strong
,
,
Fermi resonance between
and
at
,
interactions between
of
, we also investigated rotational interactions with
as well as
- and self-broadening coefficients for the
, and 2
Millimeter and Submillimeter Wave Spectroscopy of Propanal (1707.02148v2)
Oliver Zingsheim, Holger S. P. Müller, Frank Lewen, Jes K. Jørgensen, Stephan Schlemmer
2017-07-07
The rotational spectra of the two stable conformers syn- and gauche-propanal (CH
-conformer were analyzed. The newly obtained spectroscopic parameters yield better predictions, thus fulfill sensitivity and resolution requirements in new astronomical observations in order to unambiguously assign pure rotational transitions of propanal. This is demonstrated on a radio astronomical spectrum from the Atacama Large Millimeter/submillimeter Array Protostellar Interferometric Line Survey (ALMA-PILS). In particular, an accurate description of observed splittings, caused by internal rotation of the methyl group in the
-conformers, is reported. The rotational spectrum of propanal is of additional interest because of its two large amplitude motions pertaining to the methyl and the aldehyde group, respectively.
Deep neural networks for classifying complex features in diffraction images (1903.02779v3)
Julian Zimmermann, Bruno Langbehn, Riccardo Cucini, Michele Di Fraia, Paola Finetti, Aaron C. LaForge, Toshiyuki Nishiyama, Yevheniy Ovcharenko, Paolo Piseri, Oksana Plekan, Kevin C. Prince, Frank Stienkemeier, Kiyoshi Ueda, Carlo Callegari, Thomas Möller, Daniela Rupp
2019-03-07
Intense short-wavelength pulses from free-electron lasers and high-harmonic-generation sources enable diffractive imaging of individual nano-sized objects with a single x-ray laser shot. The enormous data sets with up to several million diffraction patterns represent a severe problem for data analysis, due to the high dimensionality of imaging data. Feature recognition and selection is a crucial step to reduce the dimensionality. Usually, custom-made algorithms are developed at a considerable effort to approximate the particular features connected to an individual specimen, but facing different experimental conditions, these approaches do not generalize well. On the other hand, deep neural networks are the principal instrument for today's revolution in automated image recognition, a development that has not been adapted to its full potential for data analysis in science. We recently published in Langbehn et al. (Phys. Rev. Lett. 121, 255301 (2018)) the first application of a deep neural network as a feature extractor for wide-angle diffraction images of helium nanodroplets. Here we present the setup, our modifications and the training process of the deep neural network for diffraction image classification and its systematic benchmarking. We find that deep neural networks significantly outperform previous attempts for sorting and classifying complex diffraction patterns and are a significant improvement for the much-needed assistance during post-processing of large amounts of experimental coherent diffraction imaging data.
Spectroscopic parameters for silacyclopropynylidene, SiC, from extensive astronomical observations toward CW Leo (IRC +10216) with the Herschel satellite (1112.0106v2)
H. S. P. Müller, J. Cernicharo, M. Agúndez, L. Decin, P. Encrenaz, J. C. Pearson, D. Teyssier, L. B. F. M. Waters
2011-12-01
A molecular line survey has been carried out toward the carbon-rich asymptotic giant branch star CW Leo employing the HIFI instrument on board of the Herschel satellite. Numerous features from 480 GHz to beyond 1100 GHz could be assigned unambiguously to the fairly floppy SiC
Magnetic excitations in the trimeric compounds ACu(PO
) (A = Ca, Sr, Pb) (1903.04967v1)
M. Georgiev, H. Chamati
2019-03-11
We study the magnetic excitations of the trimeric magnetic compounds A
Ultra-fast Anisotropy Control in Photoelectron Spectra: A Two-Pulse Strategy (1903.04198v1)
R. Chamakhi, M. Telmini, O. Atabek, E. Charron
2019-03-11
Coherence among rotational ion channels during photoionization is exploited to control the anisotropy of the resulting photoelectron angular distributions. The strategy refers to a robust and single parameter control using two ultra-short light pulses delayed in time for the ionization scheme. The first pulse prepares a superposition of ion rotational states, whereas the second pulse serves as a probe that gives access to a measure and control of the molecular asymmetry parameter {\beta} for individual rotational channels. This is achieved by tuning the time delay between the pulses leading to channel interferences that can be turned from constructive to destructive. The illustrative example is the ionization of the E(1{\Sigma}g+) state of Li2. Quantum wave packet evolutions are conducted including both electronic and nuclear degrees of freedom to reach angle-resolved photoelectron spectra. The most important achievement is the depiction of a simple interference model based on coherent phase accumulation during the field-free dynamics between the two pulses. This is precisely exploited to control photoelectron angular distributions from almost isotropic, to marked anisotropic.
Determination of the Electric Dipole Moment of a Molecule from Density Functional Theory Calculations (1708.03834v3)
Byeong June Min
2017-08-13
Density functional theory (DFT) calculation has had huge success as a tool capable of predicting important physical and chemical properties of condensed matter systems. We calculate the electric dipole moment of a molecule by using the differential electron density with respect to the superimposed electron density of the free atoms, exploiting the cancellation of DFT errors. Our results on a range of molecules show an excellent agreement with experiments.
