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

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

To date several fluoride containing diatomic molecules have been discovered in the Interstellar medium (ISM) with searches undertaken for both CaF and MgF.

The range of data available for these two molecules is almost identical: hence if you are working in a pair you would be able to share expertise and cross-check each other's work whilst at the same time having a molecule to work on yourself.

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 would be to undertake molecular spectroscopy calculations to produce a line list (list of wavelengths with corresponding intensities) which could then be used by astronomers for detection. 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 transitions (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)

Another possibility is to undertake calculations to investigate possible laser cooling applications.

CaF is also of interest in terms of Zeeman splitting: there are possibilities for computing Zeeman-split spectra.

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

*Initial literature for students:*

- http://www.exomol.com/
- http://kkrk.chem.elte.hu/marvelonline/index.php
- Exotic Fluoride Molecules in IRC+10216: Confirmation of AlF and Searches for MgF and CaF, Ziurys et al. (1994), JournalAstrophysical Journal, Volume 433
- High resolution UV laser spectroscopy of CaF: Rotational analysis of the C2Π-X2Σ+ (0, 0) system, Ernst et al. (1992), Journal of Molecular Spectroscopy, Volume 153, Issues 1–2

The process of generating a line list for a diatomic molecule has been successfully done on numerous occasions by the ExoMol group. However this project is novel in that, if successful, it will provide the necessary data for astronomers to hence make detections of these molecules in space.

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

Identification of experimental data. | end of October |

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

Fitting of Experimental Data. | mid-March |

Spectra simulated. | Easter |