[English]

Prosiectau Ffiseg ar gyfer myfyrwyr bl.3 a bl.4


Disgrifiad prosiect

Chemistry of the Interstellar Medium

(supervisor: Maire Gorman)

Nature of project: data analysis, software

Available to students on full-time physics degree schemes or joint students.

Project description and methodology

The molecules of OH+, OH-, CF and CF+ are of interest for the inter-stellar medium (ISM).

The nature of this project is molecular spectroscopy/quantum chemistry: no prior knowledge is needed but a keen interest in learning relevant theory is essential. Please speak to Maire beforehand if you are interested.

The overall aim of this project is to produce line lists (list of wavelengths with corresponding intensities) for these species to assist astronomers with detection.

The steps required to calculate an accurate and complete line list are detailed below.

For this particular project, students are firstly required to undertake a literature search to identify diatomic molecules of interest in volcanoes.

1. Literature review of existing experimental data and previous theoretical calculations.

2. Collect Dunham and Spectroscopic constants and hence produce a list of energies using a Dunham Expansion/PGOPHER.

3. Undertake a MARVEL analysis to check the self-consistency of measured experimental transions (http://kkrk.chem.elte.hu/marvelonline/) and hence produce a list of energies.

4. Compare the list of energies produced by (2) and (3).

5. Calculate Ab initio curves (Potential Energy curves, Dipole moment curves, spin-orbit curves, electronic angular momentum curves) using GAUSSIAN software.

6. Using the list of energies derived, fit analytical Potential energy functions (e.g. Morse).

7. Fit analytical functions to dipole moment, spin-orbit and Electronic-Angular momentum Ab initio curves (step 5).

8. Produce unrefined spectra using only Ab initio calculations (5).

9. Produce refined spectra using fitted functions (6, 7).

A successful project will develop beyond the above in one/some of the following directions:
In order to pass the project, I would expect students to at least successfully undertake steps 1, 2, 6, 8, 9 .

For a student aiming higher I would expect step 7 to be undertaken and/or steps 3 & 4.

Automate the process of fitting analytical curves (steps 6, 7).

Automate aspects of step 3.

When considering where to take your project, please bear in mind the time available. It is preferable to do fewer things well than to try many and not get conclusive results on any of them. However, sometimes it is useful to have a couple of strands of investigation in parallel to work on in case delays occur.

Additional scope or challenge if taken as a Year-4 project: Undertake step 5 (ab initio calculations)

Please speak to Maire Gorman if you consider doing this project.

Initial literature for students:

  1. http://exomol.com/
  2. http://kkrk.chem.elte.hu/marvelonline/
  3. Herschel survey of galactic OH+, H2O+, and H3O+: probing the molecular hydrogen fraction and cosmic-ray ionization rate, Indriolo et al. (2015), The Astrophysical Journal, Volume 800, Number 1
  4. Detection of extragalactic CF+ toward PKS 1830−211, Muller et al. (2016), A&A, Volume 589, L5.

Novelty, degree of difficulty and amount of assistance required

The process of producing line lists by the ExoMol group (http://exomol.com/) is well developed.

Project milestones and deliverables (including timescale)

milestoneto be completed by
Identification of experimental dataChristmas
Dunham & PGOPHER list of energies produced and comparedend of February
Fitting of Experimental Datamid-March
Spectra simulatedEaster