Nature of project: **data analysis**, software

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

The diatomic molecule of GeO has been found in the deep atmosphere of Uranus and is a strong contender for existing in the interstellar medium as well as supernova and star-forming regions.

The overall aim of this project would be the undertake molecular spectroscopy calculations to produce a line list (list of wavelengths with corresponding intensities) which could then be used by astronomers for detection.

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.

A molecular line list is a list of wavelengths and corresponding intensities for a molecule.

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:*

- http://exomol.com/
- http://kkrk.chem.elte.hu/marvelonline/index.php
- Transition probability parameters for certain band systems of astrophysical molecule GeO, Rajamanickam et al. (2003), Astroparticle Physics Volume 19 (2), P299–302
- On the E1Σ+-X1Σ+ System of GeO in the Vacuum Ultraviolet Region, Appelblad et al. (1982), Physica Scripta, Volume 25, Number 6B, P933--938

The ExoMol process of producing a line list for diatomics is a well developed process.

milestone | to be completed by |
---|---|

Summary of relevant experimental data | Christmas |

Dunham & PGOPHER list of energies produced and compared | end of February |

Fitting of Experimental Data | mid-March |

Spectra simulated | Easter |