26 results on '"Syme, Anna-Maree"'
Search Results
2. ExoMol line lists -- XLIV. IR and UV line list for silicon monoxide (SiO)
- Author
-
Yurchenko, Sergei N., Tennyson, Jonathan, Syme, Anna-Maree, Adam, Ahmad Y., Clark, Victoria H. J., Cooper, Bridgette, Dobney, C. Pria, Donnelly, Shaun T. E., Gorman, Maire N., Lynas-Gray, Anthony E., Meltzer, Thomas, Owens, Alec, Qu, Qianwei, Semenov, Mikhail, Somogyi, Wilfrid, Upadhyay, Apoorva, Wright, Samuel, and Trujillo, Juan C. Zapata
- Subjects
Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - Solar and Stellar Astrophysics ,Physics - Chemical Physics - Abstract
A new silicon monoxide ($^{28}$Si$^{16}$O) 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 6 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 9 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 (SO), electronic angular momentum (EAM) and (transition) dipole moment curves. The ab initio PE and coupling curves, computed at the multireference configuration interaction (MRCI) 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 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 database.
- Published
- 2021
- Full Text
- View/download PDF
3. Full Spectroscopic Model and Trihybrid Experimental-Perturbative-Variational Line List for CN
- Author
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Syme, Anna-Maree and McKemmish, Laura K.
- Subjects
Physics - Chemical Physics ,Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - Solar and Stellar Astrophysics - Abstract
Accurate line lists are important for the description of the spectroscopic nature of small molecules. While a line list for CN (an important molecule for chemistry and astrophysics) exists, no underlying energy spectroscopic model has been published, which is required to consider the sensitivity of transitions to a variation of the proton-to-electron mass ratio. Here we have developed a Duo energy spectroscopic model as well as a novel hybrid style line list for CN and its isotopologues, combining energy levels that are derived experimentally (Marvel), using the traditional/perturbative approach (Mollist), and the variational approach (from a Duo spectroscopic model using standard ExoMol methodology). The final Trihybrid ExoMol-style line list for 12C14N consists of 28,004 energy levels (6,864 experimental, 1,574 perturbative, the rest variational) and 2,285,103 transitions up to 60,000 cm-1 between the three lowest electronic states (X2Sigma+, A2Pi and B2Sigma+). The spectroscopic model created is used to evaluate CN as a molecular probe to constrain the variation of the proton-to-electron mass ratio; no overly promising sensitive transitions for extragalactic study were identified., Comment: Accepted in Monthly Notices of the Royal Astronomical Society. 13 pages, 11 figures
- Published
- 2021
- Full Text
- View/download PDF
4. Computational Infrared Spectroscopy of 958 Phosphorus-bearing Molecules
- Author
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Trujilo, Juan C. Zapata, Syme, Anna-Maree, Rowell, Keiran N., Burns, Brendan P., Clark, Ebubekir S., Gorman, Maire N., Jacob, Lorrie S. D., Kapodistrias, Panayioti, Kedziora, David J., Lempriere, Felix A. R., Medcraft, Chris, O'Sullivan, Jensen, Robertson, Evan G., Soares, Georgia G., Steller, Luke, Teece, Bronwyn L., Tremblay, Chenoa D., Sousa-Silva, Clara, and McKemmish, Laura K.
- Subjects
Astrophysics - Earth and Planetary Astrophysics ,Physics - Chemical Physics - Abstract
Phosphine is now well established as a biosignature, which has risen to prominence with its recent tentative detection on Venus. To follow up this discovery and related future exoplanet biosignature detections, it is important to spectroscopically detect the presence of phosphorus-bearing atmospheric molecules that could be involved in the chemical networks producing, destroying or reacting with phosphine. We start by enumerating phosphorus-bearing molecules (P-molecules) that could potentially be detected spectroscopically in planetary atmospheres and collecting all available spectral data. Gaseous P-molecules are rare, with speciation information scarce. Very few molecules have high accuracy spectral data from experiment or theory; instead, the best available data is from the RASCALL approach and obtained using functional group theory. Here, we present a high-throughput approach utilising established computational quantum chemistry methods (CQC) to produce a database of approximate infrared spectra for 958 P-molecules. These data are of interest for astronomy and astrochemistry (importantly identifying potential ambiguities in molecular assignments), improving RASCALL's underlying data, big data spectral analysis and future machine learning applications. However, this data will probably not be sufficiently accurate for secure experimental detections of specific molecules within complex gaseous mixtures in laboratory or astronomy settings., Comment: 36 pages, 10 figures
- Published
- 2021
- Full Text
- View/download PDF
5. An update to the MARVEL dataset and ExoMol line list for 12C2
- Author
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McKemmish, Laura K., Syme, Anna-Maree, Borsovszky, Jasmin, Yurchenko, Sergei N., Tennyson, Jonathan, Furtenbacher, Tibor, and Csaszar, Attila G.
- Subjects
Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - Solar and Stellar Astrophysics - 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. (2016, Astrophys. J. Suppl., 224, 44) 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 3Pig state. Older studies have been included following improvements in the MARVEL procedure which allow their uncertainties to be estimated. These older works in particular determine levels in the C1Pig state, the upper state of the insufficiently characterized Deslandres-d'Azambuja (C1Pig-A1Piu) band. The new compilation considers a total of 31323 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% of the transitions with intensities over 10^(-18) cm/molecule at 1000 K have frequencies determined by empirical energy levels.
- Published
- 2020
- Full Text
- View/download PDF
6. Experimental energy levels of 12C14N through MARVEL analysis
- Author
-
Syme, Anna-Maree and McKemmish, Laura K.
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,Physics - Chemical Physics - Abstract
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 8 doublet states of CN using the \Marvel{} (Measured Active Rotational-Vibrational Energy Levels) algorithm. \notrans{} transitions were validated from \nosources{} different published sources to generate \noenergy{} 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 \alert{77.3\%} from the original 11.3\%, with 92.6\% of the transitions with intensities over 10$^{-23}$ cm/molecule at 1000 K now known from experimental data. At 2000 K, 100.0\% of the partition function is recovered using only \Marvel{} energy levels, while 98.2\% is still recovered at 5000 K., Comment: Marvel data available here: http://kkrk.chem.elte.hu/marvelonline/index.php Updated line list available: http://exomol.com/
- Published
- 2020
- Full Text
- View/download PDF
7. Computational insight into diatomic molecules as probes to measure the variation of the proton-to-electron mass ratio
- Author
-
Syme, Anna-Maree and McKemmish, Laura K.
- Subjects
Physics - Atomic Physics ,Astrophysics - Cosmology and Nongalactic Astrophysics ,Physics - Chemical Physics - Abstract
Astrophysical molecular spectroscopy is an important means of searching for new physics through probing the variation of the proton-to-electron mass ratio, $\mu$. New molecular probes could provide tighter constraints on the variation of $\mu$ and better direction for theories of new physics. Here we summarise our previous paper \citep{19SyMoCu.CN} for astronomers, highlighting the importance of accurate estimates of peak molecular abundance and temperature as well as spectral resolution and sensitivity of telescopes in different regions of the electromagnetic spectrum. Whilst none of the 11 astrophysical diatomic molecules we investigated showed enhanced sensitive rovibronic transitions at observable intensities for astrophysical environments, we have gained a better understanding of the factors that contribute to high sensitivities. From our results, CN, CP, SiN and SiC have shown the most promise of all astrophysical diatomic molecules for further investigation, with further work currently being done on CN.
- Published
- 2020
- Full Text
- View/download PDF
8. Diatomic rovibronic transitions as potential probes for proton-to-electron mass ratio across cosmological time
- Author
-
Syme, Anna-Maree, Mousley, Adam, Cunningham, Maria, and McKemmish, Laura K
- Subjects
Physics - Chemical Physics ,Astrophysics - Cosmology and Nongalactic Astrophysics ,Physics - Atomic Physics - Abstract
Astrophysical molecular spectroscopy is an important method of searching for new physics through probing the variation of the proton-to-electron mass ratio, $\mu$, with existing constraints limiting variation to a fractional change of less than 10$^{-17}$/year. To improve on this constraint and therefore provide better guidance to theories of new physics, new molecular probes will be useful. These probes must have spectral transitions that are observable astrophysically and have different sensitivities to variation in the proton-to-electron mass ratio. Here, we concisely detail how astrophysical observations constrain the set of potential molecular probes and promising sensitive transitions based on how the frequency and intensity of these transitions align with available telescopes and observational constraints. Our detailed investigation focuses on rovibronic transitions in astrophysical diatomic molecules, using the spectroscopic models of 11 diatomics to identify sensitive transitions and probe how they generally arise in real complex molecules with many electronic states and fine structure. While none of the 11 diatomics investigated have sensitive transitions likely to be astrophysically observable, we have found that at high temperatures (1000 K) five of these diatomics have a significant number of low intensity sensitive transitions arising from an accidental near-degeneracy between vibrational levels in the ground and excited electronic state. This insight enables screening of all astrophysical diatomics as potential probes of proton-to-electron mass variation, with CN, CP, SiN and SiC being the most promising candidates for further investigation for sensitivity in rovibronic transitions.
- Published
- 2020
- Full Text
- View/download PDF
9. ASSESSING 27 MOLECULES FOR SENSITIVITY TO PROTON-TO-ELECTRON MASS VARIATION: STRENGTHS AND LIMITATIONS OF A HIGH-THROUGHPUT APPROACH
- Author
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McKemmish, Laura, primary and Syme, Anna-Maree, additional
- Published
- 2022
- Full Text
- View/download PDF
10. Computational Molecular Spectroscopy Towards New Physics
- Author
-
Syme, Anna-Maree
- Subjects
5102 Atomic, molecular and optical physics ,molecular spectroscopy ,340704 Theoretical quantum chemistry ,fundamental physics ,computational chemistry ,molecular line lists - Abstract
Several theories of modern physics go beyond the standard model of particle physics to describe as of yet unexplained phenomena of the universe. A common method of testing new theories of physics is using spectroscopy to compare transition positions at different times. Non-trivial calculations are required to determine the sensitivity coefficients of transitions to a variation of fundamental constants. These calculations can be done using nuclear motion programs with adequate spectroscopic models. In this work, 27 small molecules with spectroscopic models are evaluated as molecular probes to constrain the variation of the proton-to-electron mass ratio. The diatomic radical CN is used as a case study to develop and explain the construction of spectroscopic models. Over 40,000 experimental transitions from 22 unique sources were validated to generate a network of 8083 interconnected spin-rovibronic energy levels. These empirical energy levels, along with ab initio dipole moment curves have been used to construct and fit a spectroscopic model for the three lowest coupled electronic states of CN in the nuclear motion program Duo. The resultant line list is further refined in a novel hybrid style with the replacement of energy levels from empirical and perturbative sources to produce over 2.2 million transitions up to 60,000 cm-1. A comprehensive high-throughput methodology is developed to calculate the sensitivity coefficients for transitions in CN, 21 other diatomic and 5 small polyatomic molecules of astrophysical relevance. In diatomics, near degenerate vibronic levels and parity transitions within non-singlet-sigma ground states can cause enhanced transition sensitivity. Unfortunately, many of the enhanced transitions, especially those showing anomalously large sensitivities, have extremely low intensities at 100 K. Expanding to polyatomic molecules, tunnelling transitions (a natural progression from parity transitions) show enhanced sensitivity, especially combination rotation-tunnelling transitions. Enhanced transitions are compared against previous calculations, and some previously identified enhanced transitions are excluded from astrophysical consideration based on their very low intensity at 100 K. Selection criteria that consider factors both sensitivity and observability of transitions to be used as molecular probes for a variation in the proton-to-electron mass ratio are considered for both diatomic and polyatomic molecules.
- Published
- 2022
- Full Text
- View/download PDF
11. ExoMol line lists – XLIV. Infrared and ultraviolet line list for silicon monoxide (28Si16O)
- Author
-
Yurchenko, Sergei N, primary, Tennyson, Jonathan, additional, Syme, Anna-Maree, additional, Adam, Ahmad Y, additional, Clark, Victoria H J, additional, Cooper, Bridgette, additional, Dobney, C Pria, additional, Donnelly, Shaun T E, additional, Gorman, Maire N, additional, Lynas-Gray, Anthony E, additional, Meltzer, Thomas, additional, Owens, Alec, additional, Qu, Qianwei, additional, Semenov, Mikhail, additional, Somogyi, Wilfrid, additional, Upadhyay, Apoorva, additional, Wright, Samuel, additional, and Zapata Trujillo, Juan C, additional
- Published
- 2021
- Full Text
- View/download PDF
12. INVOLVING HIGH-SCHOOL STUDENTS IN COMPUTATIONAL CHEMISTRY MOLECULAR DATA GENERATION FOR EXOPLANET SPECTROSCOPY
- Author
-
McKemmish, Laura, primary, Sousa-Silva, Clara, additional, and Syme, Anna-Maree, additional
- Published
- 2021
- Full Text
- View/download PDF
13. COMPUTATIONAL INFRARED SPECTROSCOPY OF PHOSPHORUS-CONTAINING POTENTIAL BIOSIGNATURES
- Author
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Zapata Trujillo, Juan, primary, McKemmish, Laura, additional, Sousa-Silva, Clara, additional, Rowell, Keiran, additional, and Syme, Anna-Maree, additional
- Published
- 2021
- Full Text
- View/download PDF
14. IR, VISIBLE, AND UV LINE LIST OF SILICON MONOXIDE (SiO) - A HACKATHON PROJECT
- Author
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Adam, Ahmad, primary, Zapata Trujillo, Juan, additional, Yurchenko, Sergei, additional, Wright, Samuel, additional, Upadhyay, Apoorva, additional, Tennyson, Jonathan, additional, Syme, Anna-Maree, additional, Somogyi, Wilfrid, additional, Semenov, Mikhail, additional, Qu, Qianwei, additional, Owens, Alec, additional, Meltzer, Thomas, additional, Lynas-Gray, Anthony, additional, Gorman, Maire, additional, Donnelly, Shaun, additional, Dobney, Pria, additional, Cooper, Bridgette, additional, and Clark, Victoria, additional
- Published
- 2021
- Full Text
- View/download PDF
15. HYBRID LINE LIST AND SPECTROSCOPIC MODEL FOR CN
- Author
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Syme, Anna-Maree, primary and McKemmish, Laura, additional
- Published
- 2021
- Full Text
- View/download PDF
16. Full spectroscopic model and trihybrid experimental-perturbative-variational line list for CN
- Author
-
Syme, Anna-Maree, primary and McKemmish, Laura K, additional
- Published
- 2021
- Full Text
- View/download PDF
17. Computational Infrared Spectroscopy of 958 Phosphorus-Bearing Molecules
- Author
-
Zapata Trujillo, Juan C., primary, Syme, Anna-Maree, additional, Rowell, Keiran N., additional, Burns, Brendan P., additional, Clark, Ebubekir S., additional, Gorman, Maire N., additional, Jacob, Lorrie S. D., additional, Kapodistrias, Panayioti, additional, Kedziora, David J., additional, Lempriere, Felix A. R., additional, Medcraft, Chris, additional, O'Sullivan, Jensen, additional, Robertson, Evan G., additional, Soares, Georgia G., additional, Steller, Luke, additional, Teece, Bronwyn L., additional, Tremblay, Chenoa D., additional, Sousa-Silva, Clara, additional, and McKemmish, Laura K., additional
- Published
- 2021
- Full Text
- View/download PDF
18. ExoMol line lists – XLIV. Infrared and ultraviolet line list for silicon monoxide (28Si16O).
- Author
-
Yurchenko, Sergei N, Tennyson, Jonathan, Syme, Anna-Maree, Adam, Ahmad Y, Clark, Victoria H J, Cooper, Bridgette, Dobney, C Pria, Donnelly, Shaun T E, Gorman, Maire N, Lynas-Gray, Anthony E, Meltzer, Thomas, Owens, Alec, Qu, Qianwei, Semenov, Mikhail, Somogyi, Wilfrid, Upadhyay, Apoorva, Wright, Samuel, and Zapata Trujillo, Juan C
- Subjects
DIPOLE moments ,SPIN-orbit interactions ,ANGULAR momentum (Mechanics) ,POTENTIAL energy ,SILICON ,ELECTRONIC systems - Abstract
A new silicon monoxide (
28 Si16 O) 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. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
19. Experimental energy levels of 12C14N through marvel analysis
- Author
-
Syme, Anna-Maree, primary and McKemmish, Laura K, additional
- Published
- 2020
- Full Text
- View/download PDF
20. Computational Insight into Diatomic Molecules as Probes to Measure the Variation of the Proton-to-electron Mass Ratio
- Author
-
Syme, Anna-Maree, primary and McKemmish, Laura K., additional
- Published
- 2020
- Full Text
- View/download PDF
21. An update to the MARVEL data set and ExoMol line list for 12C2
- Author
-
McKemmish, Laura K, primary, Syme, Anna-Maree, additional, Borsovszky, Jasmin, additional, Yurchenko, Sergei N, additional, Tennyson, Jonathan, additional, Furtenbacher, Tibor, additional, and Császár, Attila G, additional
- Published
- 2020
- Full Text
- View/download PDF
22. Diatomic Rovibronic Transitions as Potential Probes for Proton-to-Electron Mass Ratio Across Cosmological Time
- Author
-
Syme, Anna-Maree, primary, Mousley, Adam, additional, Cunningham, Maria, additional, and McKemmish, Laura K., additional
- Published
- 2020
- Full Text
- View/download PDF
23. Experimental energy levels of 12C14N through marvel analysis.
- Author
-
Syme, Anna-Maree and McKemmish, Laura K
- Subjects
- *
ALGORITHMS , *NATURAL satellite atmospheres , *PLANETARY atmospheres , *ASTRONOMY - Abstract
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 77.3 per cent from the original 11.3 per cent, with 92.6 per cent of the transitions with intensities over 10−23 cm molecule−1 at 1000 K now known from experimental data. At 2000 K, 100.0 per cent of the partition function is recovered using only marvel energy levels, while 98.2 per cent is still recovered at 5000 K. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
24. An update to the MARVEL data set and ExoMol line list for 12C2.
- Author
-
McKemmish, Laura K, Syme, Anna-Maree, Borsovszky, Jasmin, Yurchenko, Sergei N, Tennyson, Jonathan, Furtenbacher, Tibor, and Császár, Attila G
- Subjects
- *
ASTRONOMICAL observations , *ASTRONOMICAL spectroscopy , *ASTROPHYSICS , *NATURAL satellite atmospheres , *PLANETARY atmospheres , *ASTROCHEMISTRY - 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. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
25. An update to the MARVEL data set and ExoMol line list for 12C2.
- Author
-
McKemmish, Laura K, Syme, Anna-Maree, Borsovszky, Jasmin, Yurchenko, Sergei N, Tennyson, Jonathan, Furtenbacher, Tibor, and Császár, Attila G
- Subjects
ASTRONOMICAL observations ,ASTRONOMICAL spectroscopy ,ASTROPHYSICS ,NATURAL satellite atmospheres ,PLANETARY atmospheres ,ASTROCHEMISTRY - Abstract
The spectrum of dicarbon (C
2 ) 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 for12 C2 , 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 33 Πg 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 C1 Πg state, the upper state of the insufficiently characterized Deslandres–d'Azambuja (C1 Πg –A1 Πu ) 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. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
26. Computational Molecular Spectroscopy Towards New Physics
- Author
-
Syme, Anna-Maree ; https://orcid.org/0000-0003-3813-0823
- Subjects
- computational chemistry, molecular spectroscopy, fundamental physics, molecular line lists, anzsrc-for: 340704 Theoretical quantum chemistry, anzsrc-for: 5102 Atomic, molecular and optical physics
- Abstract
Several theories of modern physics go beyond the standard model of particle physics to describe as of yet unexplained phenomena of the universe. A common method of testing new theories of physics is using spectroscopy to compare transition positions at different times. Non-trivial calculations are required to determine the sensitivity coefficients of transitions to a variation of fundamental constants. These calculations can be done using nuclear motion programs with adequate spectroscopic models. In this work, 27 small molecules with spectroscopic models are evaluated as molecular probes to constrain the variation of the proton-to-electron mass ratio. The diatomic radical CN is used as a case study to develop and explain the construction of spectroscopic models. Over 40,000 experimental transitions from 22 unique sources were validated to generate a network of 8083 interconnected spin-rovibronic energy levels. These empirical energy levels, along with ab initio dipole moment curves have been used to construct and fit a spectroscopic model for the three lowest coupled electronic states of CN in the nuclear motion program Duo. The resultant line list is further refined in a novel hybrid style with the replacement of energy levels from empirical and perturbative sources to produce over 2.2 million transitions up to 60,000 cm-1. A comprehensive high-throughput methodology is developed to calculate the sensitivity coefficients for transitions in CN, 21 other diatomic and 5 small polyatomic molecules of astrophysical relevance. In diatomics, near degenerate vibronic levels and parity transitions within non-singlet-sigma ground states can cause enhanced transition sensitivity. Unfortunately, many of the enhanced transitions, especially those showing anomalously large sensitivities, have extremely low intensities at 100 K. Expanding to polyatomic molecules, tunnelling transitions (a natural progression from parity transitions) show enhanced sensitivity, especially combination rotation-tunnelling transitions. Enhanced transitions are compared against previous calculations, and some previously identified enhanced transitions are excluded from astrophysical consideration based on their very low intensity at 100 K. Selection criteria that consider factors both sensitivity and observability of transitions to be used as molecular probes for a variation in the proton-to-electron mass ratio are considered for both diatomic and polyatomic molecules.
- Published
- 2022
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