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Ultrafast Belfast Group

Ultrafast Belfast Group
The Ultrafast Belfast Research group uses state-of-the-art laser technology to study ultrafast molecular dynamics. We are part of the Centre for Plasma Physics, at Queen's University Belfast, in Northern Ireland.  
We use femtosecond and attosecond laser pulses to initiate and control molecular motion on ultrashort timescales. By studying the ionization, electron emission, and fragmentation following irradiation with these laser pulses, we are able to study the nuclear, chiral, and electronic properties of molecules on ultrafast timescales.


14th January 2019

Real-time determination of enantiomeric andisomeric content using photoelectron ellipticaldichroism
The fast and accurate analysis of chiral chemical mixtures is crucial for many applications but remains challenging. Here we use elliptically-polarized femtosecond laser pulses at high repetition rates to photoionize chiral molecules. The 3D photoelectron angular distribution produced provides molecular fingerprints, showing a strong forward-backward asymmetry which depends sensitively on the molecular structure and degree of ellipticity. 
Continuously scanning the laser ellipticity and analyzing the evolution of the rich, multi-dimensional molecular signatures allows us to observe real-time changes in the chemical and chiral content present with unprecedented speed and accuracy. We measure the enantiomeric excess of a compound with an accuracy of 0.4% in 10 min acquisition time, and follow the evolution of a mixture with an accuracy of 5% with a temporal resolution of 3 s. This method is even able to distinguish isomers, which cannot be easily distinguished by mass-spectrometry.
7th July 2017

A New Technique for Probing Chirality via Photoelectron Circular Dichroism
With chirality playing a major role on biological processes there has been an ever increasing demand for fast highly sensitive techniques to determine the enantiomer present.  The discovery of photoelectron circular dichroism (PECD) could prove to be the answer.  Whilst conventional circular dichroism (CD) is relient on minute differences in the excitation rates (usually <0.1%); the asymmetry in photoelectron angular emission relative to laser progation, PECD, is orders of magnitude higher (typically 10%).
Ultrafast Belfast has developed a new experimental paradigm for measuring PECD with stereo detection setup used to measure the number of electrons emitted in directions parallel or anti-parallel to the progation of the ionising laser. This paper about to be published presents a proof-of-principle for this novel approach, along with the dependence of the asymmetry in camphor and fenchone on ellipicity of the laser pulse and the enantiomeric excess of the sample.  Enantiomeric excesses, with uncertainties of a few-percent, were measured in close to real time using a high repetition rate femtosecond laser.  With commerical turnkey femtosecond lasers now readily available, this compact instrument has the possiblity of becoming a stand-alone chiral analysis instrument.
5th July 2017

Ultrafast Dynamics in the DNA Building Blocks Thymidine and Thymine Initiated by Ionizing Radiation
Understanding how DNA is damaged by energetic charged particles is crucial for improving radiotherapy techniques.  This study measured the action of extreme ultraviolet (XUV) attosecond pulses on thymine and thymidine to simulate the damage caused by energetic particles to these DNA building blocks. The ultrafast processes triggered by the direct ionisation where probed using a 4 femtosecond NIR-VIS (near infrared - visible) pulse.  A number of sub 100 femtosecond transient processes were observed by measuring the yields of fragment ions with respect to the delay between the XUV pump pulse and NIR-VIS probe pulse.  
Building on the collaboration between Ultrafast Belfast and Politecnico di Milano which lead to the observation of charge migration in animo acids, this is the first time-dependent study of ultrafast dynmaics induced by the action of ionizing radiation on DNA.  It will provide a basis on which further theoritical and experimental studies can be conducted.
1st July 2016

Charge Migration Induced by Attosecond Pulses in Bio-Relevant Molecules
The sudden ionisation of a large molecule causes the sub-femtosecond migration of the postive charge throughout the system.  This migration is purely guided by electronic coherences.  Exploring the role of electron dynamics in the photo-chemistry of bio-relevant molecules will play a key role in understanding, and perhaps controlling, a number of ultrafast processes including those that lead to alteration of the biological functions of the macromolecule.  The extreme time resolution required to follow this ultrafast charge flow is provided by attosecond laser sources.

This review paper discusses the recent advances in attosecond molecular science.  Such as the first experimental evidence of charge migration in amino acids trigged by XUV attosecond pulses and the tremendous progress being made in the theortical modelling of ultrafast dynamics required to understand such experiments. 
5 April 2016

Ultrafast Belfast hosts 2nd COST XLIC WG3 meeting
From 4th-5th of April 2016, the Ultrafast Belfast group hosted the 2nd meeting of the COST action - XLIC (XUV/X-Ray Light and Fast Ions for Ultrafast Chemistry) Working Group 3. The topic of interest of this group is the control of reactivity of highly excited and/or ionized molecules through pump-probe techniques and High Harmonic spectroscopy.

The meeting proved successful in provoking thoughts and discussions between both theoretical and experimental physicists/chemists in the subject of chemical control. There were 35 paticipants from all over Europe, with 18 speakers, and 14 poster presenters.
There was even enough time to take a quick photo in the shadows of Lord Kelvin
13 January 2016

Ultrafast Belfast Student Wins Poster Prize At Recent Conference
PhD student Jordan Miles won runner-up poster prize at the RSC Spectroscopy and Dynamics Group Meeting (SDGM) at the University of Warrick from 5-7th January 2016.

The poster summarised interesting results on ultrafast non-radiative decay of gas-phase nucleosides. This research was recently published in the journal PCCP and can be found here.
13 August 2015

Ultrafast relaxation processes from first excited states in gas-phase nucleosides
The ultrafast photo-physical properties of DNA are crucial in providing a stable basis for life. The efficient internal conversion process, which converts the electronic energy in vibration energy to the surrounding environment, has been already observed in isolated bases. The present work, showing the first gas-phase measurements of electronic relaxation in DNA nucleosides, represents a natural next step in bottom-up understanding of DNA photo-physics.  
The experimental lifetime of internal conversion to the ground state is observed to be shorter about half the lifetime of the relative bases, possibly due to an additional relaxation pathway mediated by proton transfer through a sugar to base hydrogen bond. 
17 October 2014

Our Team Observes Electron Motion in a Biological Molecule on an Attosecond Timescale!
The work, reported in Science, was carried out using some of the shortest laser pulses in the world which were used as strobe lighting to track the ultrafast movement of the electrons within the nanometer-sized molecule. These attosecond laser pulses were used to initially stimulate the electrons and then to observe their resulting collective oscillations which lasted for 4300 attoseconds (billion-billionths of a second), the fastest process ever observed in a biological structure.

Explaining how electrons move on the nanoscale is crucial for the understanding of a range of processes in biology as it is this charge which initiates chemical reactions. For instance the charge produced from the interaction of ionizing radiation with DNA and its subsequent ultrafast excursions is crucial in determining the resulting damage to the DNA which can result in cell death or mutations. This knowledge is important for understanding the action of radiotherapy beams in cancer treatment. 
Being able to describe how light interacts with electrons on these timescales could also lead to the technological improvements such as solar cells which collect electrons more efficiently or faster microprocessors which use light rather than electrical signals for switching transistors.

The attosecond laser used for the research was developed at the Politecnico di Milano as part of a long-standing collaboration between Professor Mauro Nisoli and Dr Francesca Calegari (IFN-CNR), and the study of electrons in biomolecules has since 2012 been the product of a collaboration with Ultrafast Belfast.