Photodissociation dynamics of jet-cooled radicals via velocity map imaging spectroscopy

Supervisor(s)

Contact Dr Julia H. Lehman to discuss this project further informally.

Project description

Thionitrites, or s nitrosothiols, have the form RSNO, where R is any organic group. Thionitrites have an important role as a reaction intermediate in a variety of chemical systems, ranging from biological processes to the chemistry of planetary atmospheres. For example, these types of molecules are proposed to be responsible for the source of nitric oxide (NO) used for biological signalling processes in vasodilation. In Earth’s atmosphere, CH3SNO was experimentally observed as a reaction intermediate in high NOx environments following the reaction of OH with dimethylsulphide (DMS), an important step in the sulfur oxidation mechanisms towards forming aerosols and the stratospheric sulfate layer. It has also been theorized that the simplest thionitrite, SNO, could be a constituent in the atmospheres of Venus and Jupiter.

A full understanding and characterization of the SNO moiety is necessary in order to gain insight into the energetics involved in the above processes. As SNO is valence isoelectronic with NO2, a comparison of their electronic spectroscopy, bond strengths, and photodissociation dynamics could also give interesting insight into structure and bonding motifs from a fundamental physical chemistry perspective. In this project, you will install a new molecular beam source of radicals into an existing apparatus and characterize its performance.

You will use UV lasers to probe the photodissociation dynamics of small thionitrites, starting with the simplest SNO radical, giving insight into the distribution of energy in the photodissociation products using a technique called velocity map ion imaging. One example of this study from Dr Lehman’s work is the photodissociation of CH2OO, the simplest Criegee intermediate, forming CH2O + O. Here, the formaldehyde and oxygen atom can be produced in either their ground or lowest excited electronic states. By using state-selective ionization of oxygen and measuring its velocity distribution following photodissociation, combined with conservation of energy and momentum equations, the distribution of internal energy of CH2O can be derived.

This technique gives unique information about the kinetic energy of the co-fragments, distribution of internal energy, the dynamics of the photodissociation process, and even the amount of energy it takes to break the dissociating bond. You will interpret the laboratory measurements with the aid of theoretical methods, including quantum chemical calculations and spectroscopic modelling.

Entry requirements

Applications are invited from candidates with or expecting a minimum of a UK upper second class honours degree (2:1), and/or a Master's degree in a relevant science or engineering degree such as (but not limited to) chemistry, physics, electronic and electrical engineering, or mechanical engineering.

How to apply

Formal applications for research degree study should be made online through the university's website. Please state clearly in the research information section that the PhD you wish to be considered for is the 'Photodissociation dynamics of jet-cooled radicals via velocity map imaging spectroscopy’ as well as Dr Julia H. Lehman as your proposed supervisor. 

If English is not your first language, you must provide evidence that you meet the University’s minimum English Language requirements

We welcome scholarship applications from all suitably-qualified candidates, but UK black and minority ethnic (BME) researchers are currently under-represented in our Postgraduate Research community, and we would therefore particularly encourage applications from UK BME candidates. All scholarships will be awarded on the basis of merit.

If you require any further information please contact the Graduate School Office
e: maps.pgr.admissions@leeds.ac.uk