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

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

The diatomic molecule CaCl is of interest in Keenan bands and the Variable star wz cassiopeiae. The aim of this project is to calculate molecular line lists for group II chlorides.

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.

Undertake step 5 (ab initio calculations)

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.

*This project is only available as a Y3 project.*

Please speak to **Maire Gorman** (mng2) if you consider doing this project.

*Initial literature for students:*

- http://exomol.com/
- ExoMol molecular line lists - XXVI: spectra of SH and NS, Yurchenko et al. Mon. Notices Royal Astron. Soc 478 (2018) 270
- Variable calcium chloride absorption bands in WZ Cassipeiae, Keenan & Bidelman, Publications of the Astronomical Society of the Pacific (1979) Vol. 91, p. 365-367
- High-resolution FT spectrum of A2Πr - X2Σ+ band system of MgCl, Saksena et al. (2011), Indian Journal of Physics, Volume 85, Issue 3, pp.485-495

The ExoMol process of generating a line list involves well developed methodology which has been used for a whole range of diatomic molecules.

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

Identification of experimental data. | Christmas |

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

Fitting of Experimental Data | mid-March |

Spectra simulated. | Easter |