Vibration-rotation Energy Levels Research Articles

NASA Polynomial representation of molecular specific heats

So called NASA polynomials are widely used in plasma and combustion models to represent the specific heat of molecules as a function of temperature. In this work, we compute seven-term NASA polynomials for 464 molecules of which 44 are cations and 9 are anions; polynomials are not currently available for almost 200 of these species. Calculation of the NASA polynomials utilises data provided by the ExoMol database, the HITRAN database, the diatomic partition functions computed by Barklem and Collet, and the JANAF thermodynamic tables. Our results are compared against existing polynomial compilations where available, and for cases where there are multiple datasets the recommended polynomials are identified. As proposed in the original compilation, the seven-term polynomials are fitted separately for the temperature ranges 200 – 1000 K and 1000 – 6000 K. In general, different data sources give good agreement in the lower temperature range but there are significant discrepancies at higher temperatures, which can be attributed to the underlying assumptions made about highly excited rotation-vibration energy levels.

MARVEL analysis of high-resolution spectra of thioformaldehyde (H[formula omitted]CS)

We present a comprehensive analysis of the published spectroscopic literature on the main isotopologue of thioformaldehyde (1H212C32S). All reliable experimental transitions from publications over the last 42 years have been extracted and compiled into a consistent dataset with unique quantum number labelling and measurement uncertainties. The dataset covers the ground, ν1, ν2, ν3, ν4, ν5, ν6, and 2ν2 vibrational bands of H2CS. The ν4 and ν6 modes have very close band centres and consequently different data sources had incompatible vibrational assignments. Variational calculations are used as a basis to assign vibrational states of the associated transitions consistently. The transitions could then be processed using the robust MARVEL (Measured Active Rotational-Vibrational Energy Levels) procedure to produce a highly accurate set of 4254 rotation-vibration energy levels up to J=54 and 3729cm−1. The resulting set of labelled empirical-quality energies will be of significant use in the production of a hot molecular line list of H2CS, as well as other spectroscopic and radiative applications given the astrophysical importance of thioformaldehyde.

An Approach to Developing Cyanines with Upconverted Photosensitive Efficiency Enhancement for Highly Efficient NIR Tumor Phototheranostics.

Upconverted reactive oxygen species (ROS) photosensitization with one-photon excitation mode is a promising tactic to elongate the excitation wavelengths of photosensitive dyes to near-infrared (NIR) light region without the requirement of coherent high-intensity light sources. However, the photosensitization efficiencies are still finite by the unilateral improvement of excited-state intersystem crossing (ISC) via heavy-atom-effect, since the upconverted efficiency also plays a decisive role in upconverted photosensitization. Herein, a NIR light initiated one-photon upconversion heavy-atom-free small molecule system is reported. The meso-rotatable anthracene in pentamethine cyanine (Cy5) is demonstrated to enrich the populations in high vibrational-rotational energy levels and subsequently improve the hot-band absorption (HBA) efficiency. Moreover, the spin-orbit charge transfer intersystem crossing (SOCT-ISC) caused by electron donated anthracene can further amplify the triplet yield. Benefiting from the above two aspects, the 1 O2 generation significantly increases with over 2-fold improved performance compared with heavy-atom-modified method under upconverted light excitation, which obtains efficient in vivo phototheranostic results and provides new opportunities for other applications such as photocatalysis and fine chemical synthesis.

Classification of Amino Acids Using Hybrid Terahertz Spectrum and an Efficient Channel Attention Convolutional Neural Network.

Terahertz (THz) spectroscopy is the de facto method to study the vibration modes and rotational energy levels of molecules and is a widely used molecular sensor for non-destructive inspection. Here, based on the THz spectra of 20 amino acids, a method that extracts high-dimensional features from a hybrid spectrum combined with absorption rate and refractive index is proposed. A convolutional neural network (CNN) calibrated by efficient channel attention (ECA) is designed to learn from the high-dimensional features and make classifications. The proposed method achieves an accuracy of and on two testing datasets, which are and higher than the method solely classifying the absorption spectrum. The proposed method also realizes a processing speed of 3782.46 frames per second (fps), which is the highest among all the methods in comparison. Due to the compact size, high accuracy, and high speed, the proposed method is viable for future applications in THz chemical sensors.

Fine and hyperfine resolved empirical energy levels of VO

A MARVEL (measured active rotational-vibrational energy levels) analysis of the spectra of vanadium oxide (VO) is performed, involving thirteen electronic states (6 quartets and 7 doublets). 51V16O data from 14 sources are used to form three networks: hyperfine-resolved quartets, hyperfine-unresolved quartets and hyperfine-unresolved doublets. A single quartet network is formed by deperturbing the hyperfine lines and 190 lines are assigned to an intercombination 2 2Π–X 4Σ− band system in the visible region previously recorded by Hopkins et al. (J. Chem. Phys. 130 (2009) 144308), allowing the doublet and quartet networks to be merged. As a result 6 603/4 402 validated transitions/final energies were obtained from analysis of the hyperfine-resolved network and 9 087/4 712 from the unresolved. Tv energy values and other molecular constants are determined for all doublet states within the networks.

Ab initio characterization of the aluminum dimer in its X and A electronic states.

The potential energy functions of the aluminum dimer, Al2 , in its lowest-energy electronic states, X and A have been determined from ab initio calculations using the multi-reference averaged coupled-pair functional method in conjunction with the correlation-consistent basis sets up to septuple-zeta quality. The core-electron correlation, scalar relativistic, and spin-orbit effects were taken into account. The vibration-rotation energy levels for both the states of Al2 were calculated to near the "spectroscopic" accuracy. The state was unequivocally confirmed to be the electronic ground state of Al2 , and the electronic term value of the state was predicted to be 247 cm-1 . The energies and intensities of direct electronic-vibration transitions X ↔A were predicted.

Ground-state potential energy functions and vibration-rotation energy levels of beryllium lithium and its cation.

The accurate ground-state potential energy functions of the beryllium lithium dimer, BeLi, and its cation, BeLi+ , have been determined from ab initio calculations using the multi-reference averaged coupled-pair functional (MR-ACPF) method in conjunction with the correlation-consistent core-valence basis sets up to septuple-zeta quality. The importance of the electron correlation beyond the MR-ACPF level of approximation, scalar relativistic, and adiabatic effects was discussed. For BeLi+ , the similar calculation was performed using the single-reference coupled-cluster method, up to the CCSDTQ level of approximation. The vibration-rotation energy levels of the two species were predicted to near the "spectroscopic" accuracy. Strangely enough, the predicted vibrational term values do not compare well with the recent experimental data for either BeLi or BeLi+ , with discrepancies reaching as much as 20-60 cm-1 for highly excited vibrational levels.

Analysis of measured high-resolution doublet rovibronic spectra and related line lists of 12CH and 16OH.

Detailed understanding of the energy-level structure of the quantum states as well as of the rovibronic spectra of the ethylidyne (CH) and the hydroxyl (OH) radicals is mandatory for a multitude of modelling efforts within multiple chemical, combustion, astrophysical, and atmospheric environments. Accurate empirical rovibronic energy levels, with associated uncertainties, are reported for the low-lying doublet electronic states of 12CH and 16OH, using the Measured Active Rotational-Vibrational Energy Levels (Marvel) algorithm. For 12CH, a total of 1521 empirical energy levels are determined in the primary spectroscopic network (SN) of the radical, corresponding to the following seven electronic states: X 2Π, A 2Δ, B 2Σ−, C2 Σ+, D 2Π, E 2Σ+, and F 2Σ+. The energy levels are derived from 6348 experimentally measured and validated transitions, collected from 29 sources. For 16OH, the lowest four doublet electronic states, X 2Π, A 2Σ+, B 2Σ+, and C 2Σ+, are considered, and a careful analysis and validation of 15 938 rovibronic transitions, collected from 45 sources, results in 1624 empirical rovibronic energy levels. The large set of spectroscopic data presented should facilitate the refinement of line lists for the 12CH and 16OH radicals. For both molecules hyperfine-resolved experimental transitions have also been considered, forming SNs independent from the primary SNs.

MARVEL analysis of the high-resolution rovibrational spectra of H16O35Cl

The experimentally measured high-resolution rovibrational spectra of H16O35Cl, collated from 16 sources, have been analyzed using the Marvel (Measured Active Rotational–Vibrational Energy Levels) procedure. The compilation presented, the most extensive up to now, considers a total of 21464 transitions, allowing the derivation of 6277 empirical energy levels, extending up to 17161 cm−1, corresponding to 15 vibrational parent states. Experimental transitions data from three older sources, not published explicitly in the original papers, are presented for the first time; they represent about one half of all the transitions investigated.

ExoMol line lists – XLIV. Infrared and ultraviolet line list for silicon monoxide (28Si16O)

ABSTRACT A new silicon monoxide (28Si16O) line list covering infrared, visible, and ultraviolet regions called SiOUVenIR is presented. This line list extends the infrared EBJT ExoMol line list by including vibronic transitions to the $A\, {}^{1}\Pi$ and $E\, {}^{1}\Sigma ^{+}$ electronic states. Strong perturbations to the $A\, {}^{1}\Pi$ band system are accurately modelled through the treatment of six dark electronic states: $C\, {}^{1}\Sigma ^{-}$, $D\, {}^{1}\Delta$, $a\, {}^{3}\Sigma ^{+}$, $b\, {}^{3}\Pi$, $e\, {}^{3}\Sigma ^{-}$, and $d\, {}^{3}\Delta$. Along with the $X\, {}^{1}\Sigma ^{+}$ ground state, these nine electronic states were used to build a comprehensive spectroscopic model of SiO using a combination of empirical and ab initio curves, including the potential energy (PE), spin–orbit, electronic angular momentum, and (transition) dipole moment curves. The ab initio PE and coupling curves, computed at the multireference configuration interaction level of theory, were refined by fitting their analytical representations to 2617 experimentally derived SiO energy levels determined from 97 vibronic bands belonging to the X–X, E–X, and A–X electronic systems through the MARVEL (Measured Active Rotational–Vibrational Energy Levels) procedure. 112 observed forbidden transitions from the C–X, D–X, e–X, and d–X bands were assigned using our predictions, and these could be fed back into the MARVEL procedure. The SiOUVenIR line list was computed using published ab initio transition dipole moments for the E–X and A–X bands; the line list is suitable for temperatures up to 10 000 K and for wavelengths longer than 140 nm. SiOUVenIR is available from www.exomol.com and the CDS data base.

A high-resolution line list for AlO

ABSTRACT Indications of aluminium monoxide in atmospheres of exoplanets are being reported. Studies using high-resolution spectroscopy should allow a strong detection but require high-accuracy laboratory data. A marvel (measured active rotational-vibrational energy levels) analysis is performed for the available spectroscopic data on 27Al16O: 22 473 validated transitions are used to determine 6485 distinct energy levels. These empirical energy levels are used to provide an improved, spectroscopically accurate version of the ExoMol ATP line list for 27Al16O; at the same time, the accuracy of the line lists for the isotopically substituted species 26Al16O, 27Al17O, and 27Al18O is improved by correcting levels in line with the corrections used for 27Al16O. These line lists are available from the ExoMol data base at www.exomol.com.

An improved rovibrational linelist of formaldehyde, H[formula omitted]C[formula omitted

Published high-resolution rotation-vibration transitions of H212C16O, the principal isotopologue of methanal, are analyzed using the MARVEL (Measured Active Rotation-Vibration Energy Levels) procedure. The literature results are augmented by new, high-accuracy measurements of pure rotational transitions within the ground, ν3,ν4, and ν6 vibrational states. Of the 16 596 non-redundant transitions processed, which come from 43 sources including the present work, 16 403 could be validated, providing 5029 empirical energy levels of H212C16O with statistically well-defined uncertainties. All the empirical rotational-vibrational energy levels determined are used to improve the accuracy of ExoMol’s AYTY line list for hot formaldehyde. The complete list of collated experimental transitions, the empirical energy levels determined, as well as the extended and improved line list are provided as Supplementary Material.

Magnetically active terahertz wavefront control and superchiral field in a magneto-optical Pancharatnam-Berry metasurface.

Nowadays, the manipulation of the chiral light field is highly desired to characterize chiral substances more effectively, since the chiral responses of most molecules are generally weak. Terahertz (THz) waves are related to the vibration-rotational energy levels of chiral molecules, so it is significant to actively control and enhance the chirality of THz field. Here, we propose a metal/magneto-optical (MO) hybrid Pancharatnam-Berry (PB) phase structure, which can serve as tunable broadband half-wave plate and control the conversion of THz chiral states with the highest efficiency of over 80%. Based on this active PB element, MO PB metasurfaces are proposed to manipulate THz chiral states as different behaviors: beam deflector and scanning, Bessel beam, and vortex beam. Due to the magnetic-tunablibity, these proposed MO PB metasurfaces can be turned from an "OFF" to "ON" state by changing the external magnetic field. We further investigate the near-field optical chirality and the chirality enhancement factors in far field of the chiral Bessel beam and vortex beam, achieving the superchiral field with the highest chiral enhancement factor of 40 for 0th Bessel beam. These active, high efficiency and broadband chiral PB metasurfaces have promising applications for manipulation the THz chiral light and chiroptical spectroscopic techniques.

The W2020 Database of Validated Rovibrational Experimental Transitions and Empirical Energy Levels of Water Isotopologues. II. H217O and H218O with an Update to H216O

The W2020 database of validated experimental transitions and accurate empirical energy levels of water isotopologues, introduced in the work of Furtenbacher et al. [J. Phys. Chem. Ref. Data 49, 033101 (2020)], is updated for H216O and newly populated with data for H217O and H218O. The H217O/H218O spectroscopic data utilized in this study are collected from 65/87 sources, with the sources arranged into 76/99 segments, and the data in these segments yield 27 045/66 166 (mostly measured) rovibrational transitions and 5278/6865 empirical energy levels with appropriate uncertainties. Treatment and validation of the collated transitions of H216O, H217O, and H218O utilized the latest, XML-based version of the MARVEL (Measured Active Rotational-Vibrational Energy Levels) protocol and code, called xMARVEL. The empirical rovibrational energy levels of H217O and H218O form a complete set through 3204 cm−1 and 4031 cm−1, respectively. Vibrational band origins are reported for 37 and 52 states of H217O and H218O, respectively. The spectroscopic data of this study extend and improve the data collated by an International Union of Pure and Applied Chemistry Task Group in 2010 [J. Tennyson et al., J. Quant. Spectrosc. Radiat. Transfer 110, 2160 (2010)] as well as those reported in the HITRAN2016 information system. Following a minor but significant update to the W2020-H216O dataset, the joint analysis of the rovibrational levels for the series H216O, H217O, and H218O facilitated development of a consistent set of labels among these three water isotopologues and the provision of accurate predictions of yet to be observed energy levels for the minor isotopologues using the combination of xMARVEL results and accurate variational nuclear-motion calculations. To this end, 9925/8409 pseudo-experimental levels have been derived for H217O/H218O, significantly improving the coverage of accurate lines for these two minor water isotopologues up to the visible region. The W2020 database now contains almost all of the transitions, apart from those of HD16O, required for a successful spectroscopic modeling of atmospheric water vapor.

Experimental energy levels of 12C14N through marvel analysis.

The cyano radical (CN) is a key molecule across many different factions of astronomy and chemistry. Accurate, empirical rovibronic energy levels with uncertainties are determined for eight doublet states of CN using the marvel (Measured Active Rotational-Vibrational Energy Levels) algorithm. 40 333 transitions were validated from 22 different published sources to generate 8083 spin-rovibronic energy levels. The empirical energy levels obtained from the marvel analysis are compared to current energy levels from the mollist line list. The mollist transition frequencies are updated with marvel energy level data which brings the frequencies obtained through experimental data up to 77.3percent from the original 11.3percent, with 92.6percent of the transitions with intensities over 10-23 cm molecule-1 at 1000K now known from experimental data. At 2000K, 100.0percent of the partition function is recovered using only marvel energy levels, while 98.2percent is still recovered at 5000K.

An update to the MARVEL data set and ExoMol line list for 12C2

ABSTRACT The spectrum of dicarbon (C2) is important in astrophysics and for spectroscopic studies of plasmas and flames. The C2 spectrum is characterized by many band systems with new ones still being actively identified; astronomical observations involve eight of these bands. Recently, Furtenbacher et al. presented a set of 5699 empirical energy levels for 12C2, distributed among 11 electronic states and 98 vibronic bands, derived from 42 experimental studies and obtained using the MARVEL (Measured Active Rotational-Vibrational Energy Levels) procedure. Here, we add data from 13 new sources and update data from 5 sources. Many of these data sources characterize high-lying electronic states, including the newly detected 3 3Πg state. Older studies have been included following improvements in the MARVEL procedure that allow their uncertainties to be estimated. These older works in particular determine levels in the C 1Πg state, the upper state of the insufficiently characterized Deslandres–d’Azambuja (C 1Πg–A 1Πu) band. The new compilation considers a total of 31 323 transitions and derives 7047 empirical (marvel) energy levels spanning 20 electronic and 142 vibronic states. These new empirical energy levels are used here to update the 8states C2 ExoMol line list. This updated line list is highly suitable for high-resolution cross-correlation studies in astronomical spectroscopy of, for example, exoplanets, as 99.4 per cent of the transitions with intensities over 10−18 cm molecule−1 at 1000 K have frequencies determined by empirical energy levels.

LED based Fourier transform absorption spectroscopy of H217O in the 14900–15600 cm−1 spectral region

The vibration-rotation absorption spectrum of 17O-enriched water vapor in the range 14900–15600 cm−1 was recorded for the first time by a Fourier Transform Spectrometer coupled to a multi-pass White-type cell providing an optical path length of 34.8 m at room temperature with a spectral resolution of 0.05 cm−1 using high luminance LED (light emitting diode) light source. The high signal-to-noise ratio allowed for the accurate determination of 1047 positions of water lines, of which 661 lines were attributed to the H217O water isotopologue. The rovibrational assignment was based on new variational calculations, which allowed retrieving 285 experimental rotational-vibrational energy levels belonging to twelve vibrational states of the H217O molecule: (410), (330), (311), (231), (212), (151), (033), (052), (113), (132), (180), and (081). The 3ν1+ν2+ν3, 2ν1+3ν2+ν3 and 4ν1+ν2 vibrational bands centered, respectively, at 15325.617, 15095.166 and 15322.533 cm−1, dominate the spectrum. A detailed comparison of the H217O line intensities recorded in this study with observed literature data and with recent high-precision variational calculations showed that the calculated intensities for the (231) - (000) band are weaker by 57% than the experimental ones. The data set obtained in this study will help to improve the quality of variational calculations for water vapor.

Photoswitchable Photon Upconversion from Turn-on Mode Fluorescent Diarylethenes

Photon upconversion (UC) is one kind of anti-Stokes shift process, which generally requires a combination of two or more low-energy photons to produce one high-energy photon. However, another inter...

Empirical rovibrational energy levels of ammonia up to 7500 cm[formula omitted

The most recent version of the MARVEL (Measured Active Rotational-Vibrational Energy Levels) protocol and code is used to update and extend the list of accurately known empirical rovibrational energy levels of 14NH3 falling in the range of 0−7500 cm−1. Compared to an earlier similar study covering all the measured transitions of 14NH3 [22], the present investigation is limited to transitions with an upper energy level below 7500 cm−1, considers 82 sources (28 new) of transitions data, corrects several older assignments, and utilizes an improved validation procedure based partially on high-quality first-principles rovibrational energies. This study yields 4936 uniquely labelled empirical rovibrational energy levels, the set is complete up to 2413 cm−1. We confirm the overall high accuracy of the most recent “spectroscopic” (fitted) 14NH3 potential energy surface, C2018, up to 7500 cm−1. Investigation of energy values resulting from previous effective-Hamiltonian fits forms an important part of this study. It is established that previous effective-Hamiltonian fits, using high expansion orders in the Hamiltonian, are inaccurate for certain high rotational excitations of all vibrational parents considered. Employing the ground vibrational state as a test case, it is shown that the origin of the problem is that the observed 14NH3 spectroscopic network formed by rotational transitions and used for the effective-Hamiltonian fit contains floating components. A much improved effective-Hamiltonian fit is presented whereby the floating components are connected to the principal components of the spectroscopic network by carefully selected first-principles links. It is recommended that for all molecules the experimental set of transitions employed for an effective Hamiltonian fit should be checked for floating components and extra care be exercised if they exist, as in these cases the adequate reproduction of the transitions does not automatically mean that the energies derived from the effective-Hamiltonian parameters are correct as well. The connectivity problem of measured spectroscopic networks becomes more and more pronounced as the order of the Hamiltonian is increased.

Water vapor absorption between 5690 and 8340 cm−1: Accurate empirical line centers and validation tests of calculated line intensities

An accurate empirical list of 57,995 transitions is constructed for natural water in the 5690–8340 cm−1 near infrared region (1.76–1.20 µm). The new list represents an updated version of the list reported in Mikhailenko et al. (2016). The spectral range is extended to lower energy and the transition frequencies benefited from a series of recent measurements by comb-assisted cavity ring down spectroscopy (CA-CRDS).The line list construction uses as starting point the variational line lists computed on the basis of the results of Schwenke and Partridge for the six most abundant water isotopologues (H216O, H218O, H217O, HD16O, HD18O, HD17O). Variational line positions are replaced by position values calculated from empirical rotation-vibration energy levels. The set of required empirical energy levels is improved in accuracy and enlarged, in particular for the minor isotopologues. A large number of energy levels and thus transition frequencies, relying on spectra recorded by CA-CRDS, have accuracy on the order of 10−4 cm−1. All the transitions are provided with unique vibrational labeling supported by effective Hamiltonian calculations in case of ambiguity.A detailed comparison is presented with the list of natural water included in the HITRAN2016 database and with the very recent H216O and H218O lists reported in Conway et al. (2020). The advantage of our list in terms of line position accuracy is demonstrated and illustrated by direct comparison with CRDS recordings at disposal. Intensity comparison shows a general agreement but a number of weaknesses of the most recent intensity calculations are evidenced. All the considered theoretical line lists include a few bands (e.g. 4ν2, 5ν2, ν1+2ν2 and ν1+3ν2) with intensities deviating significantly from the observations.