Instruments

We are a laser spectroscopy and excited-state dynamics research group. Our lab designs and builds advanced instrumentation, drawing on laser spectroscopy, ion mobility spectrometry, mass spectrometry, and velocity-map imaging. We also work with the group of Prof. Steve Meech to conduct condensed-phase ultrafast spectroscopy (femtosecond fluorescence upconversion, transient absorption, time-resolved infrared), ideally seeking to compare with gas-phase data to understand the impact of solvation.

Laser Systems

Our group has three laser systems:

● EKSPLA NT-342B OPO, producing 5 ns pulses spanning 2000-266 nm - this is the workhorse for action spectroscopy - EPSRC EP/W018691/1 to JNB
● PHAROS-PH2-UP femtosecond laser (≈90 fs pulse duration at 1030 nm, single shot to 200 kHz) with OPA (ORPHEUS-NEO-UP, near-IR to near-UV) and HIRO (515, 343 nm) module - EPSRC Core Equipment Award (2025/2026) to JNB
● Continuum Surelite Nd:YAG with 532/355 nm generation crystals

The group of Prof. Steve Meech has other femtosecond laser systems, including a Spectra-Phyics Ti:Sapp oscllator with a variety of OPAs. These are setup for condensed phase ultrafast expeirments.

PASTA - Photoinduced Action Spectroscopy Targeting Anions

PASTA instrument at UEA
Illustration of the PASTA instrument developed at UEA. This image was taken from our Rev. Sci. Instrum. instrument paper, which has a complete description of the ToF and VMI regions.

The PASTA (Photoinduced Action Spectroscopy Targeting Anions) instrument, shown to the left, was developed as part of EPSRC New Investigator Award (EP/W018691/1). The central goal is a highly-flexible platform to perform isomer-specific spectroscopy (photoelectron, photodetachment, photoisomerisation, and photodissociation) of anions by combining tandem ion mobility spectrometry, quadrupole ion trapping, time-of-flight mass spectrometry, and orthogonal photoelectron velocity-map imaging. It has been developed around standard 6 in. and 2-3/4 in. ConFlat flanges and the use of 3D printable mounts and holders, allows the instrument to be adapted easily to incorporate a variety of ion sources or additional sectors as applications demand.

Features are:

● Coupling with electrospray ionisation, tandem ion mobility spectrometry, and ion trapping, allowing for photoisomerisation action spectroscopy, isomer-specific photodetachment and photoelectron spectroscopies (in both frequency and time domains), and the photogeneration, separation, and study of transient intermediates that survive for a few milliseconds or longer.
● Capabilities to perform both photodetachment (resolution limited by laser bandwidth) and photoelectron spectroscopies on anions and to record photoelectron spectra simultaneously when acquiring a photodetachment spectrum (i.e., frequency-resolved photoelectron spectroscopy).
● The versatility to generate ions from easily interchangeable hard- and soft-plasma pulsed valve sources for astrochemical applications. Using these pulsed-valve sources, the instrument should be capable of studying small anions (a few atoms) to moderately sized anions (≈60 atoms) through time-of-flight mass spectrometry.
● Velocity-map imaging detection to acquire electron kinetic energies without discrimination effects and to record angular information about photoelectrons.
● The capacity to disentangle prompt and delayed (e.g., thermionic emission) signals in both photoelectron and photodetachment spectra by time-gating the photoelectron detector (≈5 ns time resolution) relative to the laser.



PISA - PhotoIsomerisation Action Spectroscopy

Compared with photodissociation, photodetachment, and photoelectron spectroscopies, the technique of photoisomerisation action spectroscopy (PISA) is an emerging technique. PISA spectroscopy, which was pioneering by the Bieske group at The University of Melbourne in Australia, couples tandem ion mobility mass spectrometry with laser spectroscopy to achieve both isomer-specific spectroscopy and the ability to monitor photoisomerisation directly. The clear identification and separation of isomers, and the ability to monitor photoisomerisation, has conventionally been challenging in gas-phase experiments. Our PISA spectroscopy instrument, much of which was kindly donated by Prof. Evan Bieske, is shown below. The instrument was rebuilt at UEA with new computer control, data acquisition, and vacuum pumping.
PISA spectroscopy instrument at UEA
Illustration of the PISA spectroscopy instrument at UEA. The perspex box is divided into two regions, IMS1 and IMS2, allowing for tandem ion mobility spectrometry.

PISA spectroscopy relies on isomeric ions becoming separated in space (which is related to arrival time or 'traversal time') when the ions are propelled through a drift region containing a buffer gas at a pressure of ~5-10 mbar under the influence of a weak electric field (~44 V/cm). The buffer gas is either N2 or N2 seeded with a trace amount of a dopant such as propan-2-ol or SF6.