Physics projects for Y3 and Y4 students

Project description

Molecular Spectroscopy of Brown Dwarfs

(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

This project would suit an ambitious year 4 student or pair of ambitious year 3 students.

Brown dwarfs are so-called “failed stars” which have not reached the required mass in order to ignite Hydrogen fusion. Extensive work is being done on modelling the atmospheres of these faint objects.

L-type Brown Dwarfs are characterized by the inclusion of diatomic metal hydrides such as CrH, FeH and CaH. To date, SrH has not been detected but is a potential candidate: hence analysis of existing experimental data would open the possibility for future detection.

Diatomic Constants (DCs) are constants fitted by experimentalists which can be used to generate a list of energies. One potential drawback with DCs is that they do not take into account perturbations and interactions between electronic states within a molecule.

MARVEL analysis can potentially circumvent this issue: the process involves using online software to build "spectroscopic networks" of energy levels from experimentally measured wavelengths.

The list of energies produced by using DCs and MARVEL process can be compared.

A successful project will develop beyond the above in one/some of the following directions:
As baseline I would expect student to undertake analysis of data for SrH and one electronic system of FeH. More ambitious students can aim to analyse all electronic states for which experimental data is available.

A different type of work would be to then fit potential energy curves to derived energy levels using Duo programme. This is a challenging type of fitting.

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: FeH is a hugely challenging molecule to work on-however it is vitally important for modelling of L dwarfs. SrH is much simpler and hence would serve as “training” in undertaking a MARVEL analysis.

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

Initial literature for students:

  1. http://kkrk.chem.elte.hu/marvelonline/index.php
  2. MARVEL Analysis of the Measured High-resolution Rovibronic Spectra of 90Zr160, McKemmish et al. (2018), The Astrophysical Journal, 867 (1), Article 33
  3. High resolution emission spectroscopy of the E 2 P –X 2 R + transition of SrH and SrD, Ram et al. (2012), Journal of Molecular Spectroscopy, 271, P15–19
  4. Line Intensities and Molecular Opacities of the FeH F 4Δi–X 4Δi Transition, Dulick et al. (2003), The Astrophysical Journal, 594(1), P651-663,

Novelty, degree of difficulty and amount of assistance required

No previous knowledge of molecular spectroscopy is required but a keen interest is essential.

Project milestones and deliverables (including timescale)

milestoneto be completed by
Overview diagram of experimental data availableChristmas
Collection of spectroscopic constants and Dunham analysisend of February
MARVEL analysis of ground electronic statemid-March
MARVEL analysis of upper electronic systemsEaster