2,276 research outputs found
Hybrid variation-perturbation method for calculating rovibrational energy levels of polyatomic molecules
A procedure for calculation of rotation-vibration states of medium sized
molecules is presented. It combines the advantages of variational calculations
and perturbation theory. The vibrational problem is solved by diagonalizing a
Hamiltonian matrix, which is partitioned into two sub-blocks. The first,
smaller sub-block includes matrix elements with the largest contribution to the
energy levels targeted in the calculations. The second, larger sub-block
comprises those basis states which have little effect on these energy levels.
Numerical perturbation theory, implemented as a Jacobi rotation, is used to
compute the contributions from the matrix elements of the second sub-block.
Only the first sub-block needs to be stored in memory and diagonalized.
Calculations of the vibrational-rotational energy levels also employ a
partitioning of the Hamiltonian matrix into sub-blocks, each of which
corresponds either to a single vibrational state or a set of resonating
vibrational states, with all associated rotational levels. Physically, this
partitioning is efficient when the Coriolis coupling between different
vibrational states is small. Numerical perturbation theory is used to include
the cross-contributions from different vibrational states. Separate individual
sub-blocks are then diagonalized, replacing the diagonalization of a large
Hamiltonian matrix with a number of small matrix diagonalizations. Numerical
examples show that the proposed hybrid variational-perturbation method greatly
speeds up the variational procedure without significant loss of precision for
both vibrational-rotational energy levels and transition intensities. The
hybrid scheme can be used for accurate nuclear motion calculations on molecules
with up to 15 atoms on currently available computers.Comment: Molecular Physics (Handy Special Issue), in pres
Henry Bergson: intellectual and supra-intellectual intuition
В статье сопоставляются концепции интеллектуальной интуиции Декарта и суперинтеллектуальной интуиции Бергсона с целью выявить, какую роль играет интеллектуальная составляющая познания в рамках философии длительности. Акцент ставится не только на преемственности, что показано на примерах Декартового дуализма и понятия свободы воли, но также на различии, основанном на таких опорных для Бергсона пунктах, как творчество и качественные различия, что позволяет говорить о переходе к «философии жизни».The article compares Descartes’ concept of intellectual intuition and Bergson’s concept of supra-intellectual intuition to identify the role of the intellectual component of cognition in the philosophy of duration. Emphasis is put not only on the continuity of philosophical views, as shown in the examples of Descartes' dualism and notion of free will, but also on the difference based on these reference points for Bergson, as creativity and qualitative differences, which suggests a passage to “Philosophy of Life.
MARVEL analysis of the measured high-resolution rovibronic spectra of the calcium monohydroxide radical (CaOH)
The calcium monohydroxide radical (CaOH) is an important astrophysical
molecule relevant to cool stars and rocky exoplanets, amongst other
astronomical environments. Here, we present a consistent set of highly accurate
rovibronic (rotation-vibration-electronic) energy levels for the five lowest
electronic states (\tilde{X}\,^2\Sigma^+, \tilde{A}\,^2\Pi,
\tilde{B}\,^2\Sigma^+, \tilde{C}\,^2\Delta, \tilde{D}\,^2\Sigma^+) of
CaOH. A comprehensive analysis of the published spectroscopic literature on
this system has allowed 1955 energy levels to be determined from 3204
rovibronic experimental transitions, all with unique quantum number labelling
and measurement uncertainties. The dataset covers rotational excitation up to
for molecular states below 29\,000~cm. The analysis was
performed using the MARVEL algorithm, which is a robust procedure based on the
theory of spectroscopic networks. The dataset provided will significantly aid
future interstellar, circumstellar and atmospheric detections of CaOH, as well
as assisting in the design of efficient laser cooling schemes in ultracold
molecule research and precision tests of fundamental physics
ExoMol molecular line lists - XVI: The rotation-vibration spectrum of hot HS
This work presents the AYT2 line list: a comprehensive list of 114 million
HS vibration-rotation transitions computed using an
empirically-adjusted potential energy surface and an {\it ab initio} dipole
moment surface. The line list gives complete coverage up to 11000 \cm\
(wavelengths longer than 0.91 m) for temperatures up to 2000 K. Room
temperature spectra can be simulated up to 20000 \cm\ (0.5 m) but the
predictions at visible wavelengths are less reliable. AYT2 is made available in
electronic form as supplementary data to this article and at
\url{www.exomol.com}.Comment: 12 pages, 10 figures, 10 table
Collective modes of two-dimensional classical Coulomb fluids
Molecular dynamics simulations have been performed to investigate in detail
collective modes spectra of two-dimensional Coulomb fluids in a wide range of
coupling. The obtained dispersion relations are compared with theoretical
approaches based on quasi-crystalline approximation (QCA), also known as the
quasi-localized charge approximation (QLCA) in the plasma-related context. An
overall satisfactory agreement between theory and simulations is documented for
the longitudinal mode at moderate coupling and in the long-wavelength domain at
strong coupling. For the transverse mode, satisfactory agreement in the
long-wavelength domain is only reached at very strong coupling, when the cutoff
wave-number below which shear waves cannot propagate becomes small. The
dependence of the cutoff wave-number for shear waves on the coupling parameter
is obtained.Comment: 10 pages, 6 figure
Lichens of Historical Manor Parks in Northwest-central Belarus.
В результате изучения шести усадебных парков, расположенных в Минской области и взятых в качестве пробных участков, идентифицировано 119 видов лихенизированных сумчатых грибов. Парки были распределены по двум категориям: богатые видами (65‒72 вида лишайников) и бедные видами (38‒47 видов лишайников). Кластерный анализ, основанный на относительном обилии видов, показал малые различия в лихенобиоте между парками, бедными видами, и значительные различия между парками, богатыми видами. В качестве факторов, увеличивающих видовое богатство лишайников, рассматриваются наличие многочисленных старовозрастных деревьев, заболоченных участков местности, скоплений валунов, руин, а также усложненный рельеф. Главными характеристиками, описывающими различия в лихенобиоте парков, были: число редких видов, число видов накипной жизненной формы, число видов, населяющих минеральные субстраты. В то же время число видов листоватой жизненной формы, процент эпифитных видов, число видов на бетоне и гниющей древесине были сходны в изученных парках. Семь видов, в особенности Oxneria fallax, Parmelina tiliacea и Pleurosticta acetabulum, были вычленены как приуроченные по преимуществу к парковых экосистемам. Впервые для Беларуси были определены Candelaria pacifica, Lecania erysibe, L. sylvestris и Thelidium minutulum. Diplotomma alboatrum, Leptogium cyanescens и Pyrrhospora quernea были подтверждены для лихенобиоты Беларуси образцами из изученных парков. = As a result of the study of lichenized Ascomycota in six sample manor parks, situated in Minsk region, 119 species were identified. The parks belong to the two categories: species-rich (with 65–72 lichen species) and species-poor (with 38–47 species). Cluster analysis based on relative abundance of the species showed small differences between species-poor parks and significant differences between species-rich parks. The presence of numerous old-aged trees, wetlands, stone aggregations, ruins, and complicated relief are considered. as the factors, rising species richness in parks. The main characteristics making dif-ferences in lichen biota of the parks were number of rare species, number of species belonging to crustose growth form, and number of species inhabiting mineral substrata. In the same time number of foliose spe-cies, per cent of epiphytic species, number of species on concrete and wood were similar in the parks studied. Seven taxa, especially Oxneria fallax, Parmelina tiliacea, and Pleurosticta acetabulum, were distinguished as confined mostly to park ecosystems. Candelaria pacifica, Lecania erysibe, L. sylvestris, and Thelidium minutulum were recorded for the first time in Belarus. Diplotomma alboatrum, Leptogium cyanescens, and Pyrrhospora quernea were confirmed for lichen biota of Belarus by recent collections. Key words: epilithes, epiphytes, phorophyte, substratum type, thallus morphotype
A near infrared line list for \NH: Analysis of a Kitt Peak spectrum after 35 years
A Fourier Transform (FT) absorption spectrum of room temperature NH3 in the
region 7400 - 8600 cm-1 is analysed using a variational line list and ground
state energies determined using the MARVEL procedure. The spectrum was measured
by Dr Catherine de Bergh in 1980 and is available from the Kitt Peak data
center. The centers and intensities of 8468 ammonia lines were retrieved using
a multiline fitting procedure. 2474 lines are assigned to 21 bands providing
1692 experimental energies in the range 7000 - 9000 cm-1. The spectrum was
assigned by the joint use of the BYTe variational line list and combination
differences. The assignments and experimental energies presented in this work
are the first for ammonia in the region 7400 - 8600 cm-1, considerably
extending the range of known vibrational-excited statesComment: 27 pages, 6 table, 5 figures. Accepted for publication in Journal of
Molecular Spectroscop
До питання про характер стосунків слов’ян з носіями салтово-маяцької культури в лісостепу
В статті розглядається питання про характер контактів між слов’янами та носіями салтово-маяцької культури в Донецькому лісостепу. Розглянуто дві точки зору на цю проблему – про мирне співіснування і про військову основу стосунків. А також проаналізовано елементи матеріальної культури, котрі свідчать на користь таких стосунків.
В статье рассматривается вопрос о характере контактов между славянами и носителями салтово-маяцкой культуры в Донецкой лесостепи. Рассмотрены две точки зрения на эту проблему - о мирном сосуществовании и о военной основе отношений. А также проанализированы элементы материальной культуры, которые свидетельствуют в пользу таких отношений.
The article deals with the problem of contacts between Slavs and people of Saltov culture in the Donetsk steppe. Both points of view on this issue - the peaceful coexistence and the military relations were considered. Also the elements of material culture, which demonstrate the benefits of such relationships were analyzed
Physical optics modeling of 2D dielectric lenses
Cataloged from PDF version of article.We propose an advanced physical optics formulation for the accurate modeling of dielectric lenses used in
quasi-optical systems of millimeter, submillimeter, and infrared wave applications. For comparison, we obtain
an exact full-wave solution of a two-dimensional lens problem and use it as a benchmark for testing and validation
of asymptotic models being considered. © 2009 Optical Society of Americ
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