scholarly journals The Leiden Atomic and Molecular Database (LAMDA): Current Status, Recent Updates, and Future Plans

Atoms ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 15 ◽  
Author(s):  
Floris van der Tak ◽  
François Lique ◽  
Alexandre Faure ◽  
John Black ◽  
Ewine van Dishoeck
Keyword(s):  
Cross Sections ◽  
Far Infrared ◽  
Molecular Data ◽  
Rate Coefficients ◽  
Current Status ◽  
Spectroscopic Information ◽  
Recent Developments ◽  
Collisional Rate Coefficients ◽  
Near Future ◽  
Collisional Rate

The Leiden Atomic and Molecular Database (LAMDA) collects spectroscopic information and collisional rate coefficients for molecules, atoms, and ions of astrophysical and astrochemical interest. We describe the developments of the database since its inception in 2005, and outline our plans for the near future. Such a database is constrained both by the nature of its uses and by the availability of accurate data: we suggest ways to improve the synergies among users and suppliers of data. We summarize some recent developments in computation of collisional cross sections and rate coefficients. We consider atomic and molecular data that are needed to support astrophysics and astrochemistry with upcoming instruments that operate in the mid- and far-infrared parts of the spectrum.

scholarly journals Water in star- and planet-forming regions

2012 ◽  
Vol 370 (1968) ◽  
pp. 2778-2802 ◽  
Author(s):  
Edwin A. Bergin ◽  
Ewine F. van Dishoeck
Keyword(s):  
Water Vapour ◽  
Reaction Rates ◽  
Molecular Data ◽  
Rate Coefficients ◽  
Space Observatory ◽  
Water Tracing ◽  
Successful Launch ◽  
Collisional Rate Coefficients ◽  
Collisional Rate ◽  
Chemical Reaction Rates

In this paper, we discuss the astronomical search for water vapour in order to understand the disposition of water in all its phases throughout the processes of star and planet formation. Our ability to detect and study water vapour has recently received a tremendous boost with the successful launch and operation of the Herschel Space Observatory . Herschel spectroscopic detections of numerous transitions in a variety of astronomical objects, along with previous work by other space-based observatories, will be threaded throughout this paper. In particular, we present observations of water tracing the earliest stage of star birth where it is predominantly frozen as ice. When a star is born, the local energy release by radiation liberates ices in its surrounding envelope and powers energetic outflows that appear to be water factories. In these regions, water plays an important role in the gas physics. Finally, we end with an exploration of water in planet-forming discs surrounding young stars. The availability of accurate molecular data (frequencies, collisional rate coefficients and chemical reaction rates) is crucial to analyse the observations at each of these steps.

Rotational de-excitations of C3H+ (1Σ+) by collision with He: new ab initio potential energy surface and scattering calculations

2020 ◽  
Vol 494 (4) ◽  
pp. 5675-5681 ◽  
Author(s):  
Sanchit Chhabra ◽  
T J Dhilip Kumar
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Ab Initio ◽  
Cross Sections ◽  
Energy Surface ◽  
Molecular Ions ◽  
Basis Set ◽  
Rate Coefficients ◽  
Close Coupling ◽  
Collisional Rate Coefficients

ABSTRACT Molecular ions play an important role in the astrochemistry of interstellar and circumstellar media. C3H+ has been identified in the interstellar medium recently. A new potential energy surface of the C3H+–He van der Waals complex is computed using the ab initio explicitly correlated coupled cluster with the single, double and perturbative triple excitation [CCSD(T)-F12] method and the augmented correlation consistent polarized valence triple zeta (aug-cc-pVTZ) basis set. The potential presents a well of 174.6 cm−1 in linear geometry towards the H end. Calculations of pure rotational excitation cross-sections of C3H+ by He are carried out using the exact quantum mechanical close-coupling approach. Cross-sections for transitions among the rotational levels of C3H+ are computed for energies up to 600 cm−1. The cross-sections are used to obtain the collisional rate coefficients for temperatures T ≤ 100 K. Along with laboratory experiments, the results obtained in this work may be very useful for astrophysical applications to understand hydrocarbon chemistry.

Calculations of fine-structure resolved collisional rate coefficients for the NH(X3Σ−)-He system

2011 ◽  
Vol 134 (2) ◽  
pp. 024305 ◽  
Author(s):  
Robert Toboła ◽  
Fabien Dumouchel ◽  
Jacek Kłos ◽  
François Lique
Keyword(s):  
Fine Structure ◽  
Rate Coefficients ◽  
Collisional Rate Coefficients ◽  
Collisional Rate

Collisional-Rate Coefficients for Sodiumlike Ar viii Ions

1972 ◽  
Vol 6 (1) ◽  
pp. 38-44 ◽  
Author(s):  
R. U. Datla ◽  
H. -J. Kunze ◽  
D. Petrini
Keyword(s):  
Rate Coefficients ◽  
Collisional Rate Coefficients ◽  
Collisional Rate

scholarly journals Influence of Silicon on Biocontrol Strategies to Manage Biotic Stress for Crop Protection, Performance, and Improvement

Plants ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 2163
Author(s):  
Krishan K. Verma ◽  
Xiu-Peng Song ◽  
Dan-Dan Tian ◽  
Dao-Jun Guo ◽  
Zhong-Liang Chen ◽  
...  
Keyword(s):  
Biotic Stress ◽  
Crop Improvement ◽  
Crop Protection ◽  
Essential Element ◽  
Common Element ◽  
Current Status ◽  
Pest Infestation ◽  
Recent Developments ◽  
Term Basis ◽  
Near Future

Silicon (Si) has never been acknowledged as a vital nutrient though it confers a crucial role in a variety of plants. Si may usually be expressed more clearly in Si-accumulating plants subjected to biotic stress. It safeguards several plant species from disease. It is considered as a common element in the lithosphere of up to 30% of soils, with most minerals and rocks containing silicon, and is classified as a “significant non-essential” element for plants. Plant roots absorb Si, which is subsequently transferred to the aboveground parts through transpiration stream. The soluble Si in cytosol activates metabolic processes that create jasmonic acid and herbivore-induced organic compounds in plants to extend their defense against biotic stressors. The soluble Si in the plant tissues also attracts natural predators and parasitoids during pest infestation to boost biological control, and it acts as a natural insect repellent. However, so far scientists, policymakers, and farmers have paid little attention to its usage as a pesticide. The recent developments in the era of genomics and metabolomics have opened a new window of knowledge in designing molecular strategies integrated with the role of Si in stress mitigation in plants. Accordingly, the present review summarizes the current status of Si-mediated plant defense against insect, fungal, and bacterial attacks. It was noted that the Si-application quenches biotic stress on a long-term basis, which could be beneficial for ecologically integrated strategy instead of using pesticides in the near future for crop improvement and to enhance productivity.

scholarly journals New H2O–H2O collisional rate coefficients for cometary applications

2020 ◽  
Vol 498 (4) ◽  
pp. 5489-5497 ◽  
Author(s):  
C Boursier ◽  
B Mandal ◽  
D Babikov ◽  
M L Dubernet
Keyword(s):  
Cross Sections ◽  
Potential Energy Surfaces ◽  
Rate Coefficients ◽  
Molecular Systems ◽  
Large Sets ◽  
Alternative Approach ◽  
Collisional Rate Coefficients ◽  
Energy Surfaces ◽  
Good Agreement

ABSTRACT We re-introduce a semiclassical methodology based on theories developed for the determination of broadening coefficients. We show that this simple and extremely fast methodology provides results that are in good agreement with results obtained using the more sophisticate MQCT approach. This semiclassical methodology could be an alternative approach which allows to provide large sets of collisional data for very complex molecular systems. It saves time both on the determination of potential energy surfaces and on the collisional dynamical calculations. In addition, this paper provides more complete sets of rotational de-excitation cross-sections and rate coefficients of H2O perturbed by a thermal average of water molecules. Those data can be used in the radiative transfer modelling of cometary atmospheres.

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