Electron driven molecular dissociation
Lead Research Organisation:
University College London
Department Name: Physics and Astronomy
Abstract
Astrophysically small molecules exist not just in quiescent cool clouds, which themselves are weakly ionized and therefore contain electrons, but also in much more active astrophysical regions such as planetary nebulae and diffuse interstellar clouds. These regions often contain significant numbers of free, quasi-thermal electrons, up to 10-4 compared to H2. These electrons can effect chemical change and drive observable spectroscopy processes (see A.J. Lim, I. Rabadan and J. Tennyson, MNRAS, 306, 473 (1999) for example); the cross sections between electrons and molecular ions are particularly large. Additionally electron molecule collisions are important elsewhere, for example they are the main driver behind planetary aurorae and many molecular masers. Models of all these regimes require data which is largely unknown and, in many cases, cannot be determined from laboratory based measurements. Over the last two decades the UCL group has developed the UK molecular R-matrix codes to provide a first principles, quantum mechanical treatment of the collision between low energy electrons and small molecules. This code has been used to treat collisions leading to rotational excitation involving important astrophysical ions (see for example A. Faure and J. Tennyson, MNRAS, 325, 443 (2001), A. Faure, J.D. Gorfinkiel and J. Tennyson, MNRAS 347, 323 (2004)). Recent observations of molecular emissions from C-shocked regions of the ISM (Jimenez-Serra et al, ApJ 650, L135 (2007)) showed that it is possible to recover local electron densities by using our electron molecule collisions calculations. Low-energy electrons also destroy molecules through dissociative recombination (DR for ions) and dissociative attachment (DA for neutrals). Cross sections for these processes are often hard to obtain. The present proposal is for a PhD student who will use the QuantemolN implementation of the UK polyatomic R- matrix code to study electron collisions with molecules of astrophysical interest and obtain dissociative cross sections. To do this the student will develop and test an add-on DA/DR estimator for Quantemol-N. A preliminary DA estimator developed by the company will provide the starting point for this work. The QuantemolN code, which will be provided by the company, is very suitable for these studies since it is an expert system which greatly increases the ease and speed with which a user can perform very technically demanding electron collision calculations. In return the student will assist the company in adding further features to this code to treat DA and DR. This project is proposed now since this feature has recently been requested by a Japanese industrial client of the company and a number of other users have expressed a strong interest. Adding to this functionality of the code is a strategic aim of Quantemol. The student will be provided training in performing electron molecule collision calculations, interpreting the results and using them in astronomical models and to interpret astronomical spectra. S/he will interact with people directly observing the processes, several of whom (for example Dr J Rawlings and Dr S Viti) are at UCL. S/he will also experience working with a small start up company which gives the opportunity to be involved both in the software development and in the interaction with other users of the code. This proposal follows a highly successful CASE studentship award to Dr HN Varambhia who used Quantemol-N to do studies on HCN, HNC, CS, CO and other astrophysically important systems (Eg Varambhia et al, Electron-impact rotational excitation of the carbon monosulfide (CS) molecule, MNRAS in press) which has been of immense benefit to the company by raising its scientific profile which led to new orders for the existing Quantemol-N package and interest in the others, from both the UK and abroad. Varambhia also added an electron impact ionization estimator to Quantemol-N.
Publications
A E Lynas-Gray
(2018)
Current State of Astrophysical Opacities: A White Paper
in Astronomical Society of the Pacific Conference Series
A Fazliev
(2010)
Computed knowledge base for description of information resources of water spectroscopy
in CEUR Workshop Proceedings
Al-Refaie, Ahmed F.
(2015)
ExoMol line lists - VIII. A variationally computed line list for hot formaldehyde
in Monthly Notices of the Royal Astronomical Society
Brigg W
(2015)
Calculated photoionization cross sections using Quantemol-N
in Japanese Journal of Applied Physics
D A Garcia-Hernandez
(2018)
A New Near-IR C-2 Linelist for an Improved Chemical Analysis of Hydrogen-deficient, Carbon-rich Giants
in Astronomical Society of the Pacific Conference Series
Harrison S
(2011)
Bound and continuum states of molecular anions C 2 H - and C 3 N -
in Journal of Physics B: Atomic, Molecular and Optical Physics
Jonathan Tennyson
(2018)
The ExoMol Project: Molecular Opacity Calculations at University College London
in Astronomical Society of the Pacific Conference Series
Kelly Ross E. A.
(2010)
Using a vibrational averaging technique to understand the role of water dimers in atmospheric absorption
in ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY
Kelly Ross E. A.
(2010)
Theoretical determined water dimer spectra in the near IR and visible regions in the atmosphere
in ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY
Kokoouline V
(2010)
Calculation of rate constants for vibrational and rotational excitation of the H + 3 ion by electron impact
in Monthly Notices of the Royal Astronomical Society
Description | The ability to photoionize molecules was added the code Quantemol-N |
Exploitation Route | The code is used extensively by others |
Sectors | Chemicals,Digital/Communication/Information Technologies (including Software),Electronics |
URL | http://www.quantemol.com |
Description | STFC CASE studentship |
Amount | £95,000 (GBP) |
Funding ID | ST/J002925 |
Organisation | Science and Technologies Facilities Council (STFC) |
Sector | Public |
Country | United Kingdom |
Start | 10/2012 |
End | 09/2016 |
Title | Databases of molecular line lists |
Description | Our molecular line lists have been collected as data. These are distributed directly from our own website and via other data centres (Strasbourg, BADC) and via other databases: HITRAN, GEISA, KIDA, BASECOL, HITEMP etc |
Type Of Material | Database/Collection of data |
Provided To Others? | Yes |
Impact | HITRAN has 200,000 users. Our data is now central to this. Other data is having an important influence in other key areas eg Exoplanet research. |
Description | Quantemol |
Organisation | Quantemol Ltd |
Country | United Kingdom |
Sector | Private |
PI Contribution | sponsorship of case studentshipd |
Collaborator Contribution | money, computer programs, help |
Impact | Quantemol product development |
Title | Quantemol-N photoionisation product |
Description | A new module was created for the Quantemol-N expert system which treats molecular photoionisation |
Type Of Technology | Software |
Year Produced | 2017 |
Impact | This has been launched as a product by industrial partner Quantemol Ltd |
URL | http://www.quantemol.com/products/quantemol-n/ |
Description | electrons driven technolgies |
Form Of Engagement Activity | A magazine, newsletter or online publication |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Health professionals |
Results and Impact | Given in 1-to-1 meetings with several (about 8) industrial visitors Impact has been via industrial partner in CASE award, Quantemol, who have gained customers |
Year(s) Of Engagement Activity | 2009,2010,2011 |