Joseph Sanderson

• Coulomb imaging of small molecules
• Mass spectrometry for nano-science applications
• Nanoparticle generation by femtosecond laser irradiation

Coulomb imaging

In his lab and at the ALLS (Advanced Laser Light Source) laboratory they can use the two most important properties of a femtosecond laser pulse, its tiny duration (1fs=one thousand million millionths of a second, which is inconceivably short to a human being but is quite normal for molecules which are used to vibrating on this kind of timescale) and its high intensity (this is partly a consequence of the shortness of the pulse because intensity is power divided by area and power is energy divided by the pulse duration).

The pulse length acts like the shutter speed of a camera allowing them take a snapshot of a molecule in motion and the intensity gives us a means to make the image. The high intensity is used to rip many electrons from the molecule (the laser light develops a momentary electric field stronger than the one which binds the electrons to the atoms) which then explodes because there are not enough electrons left to bind the positively charged atomic ions together. This is called a Coulomb explosion after the physicist Charles de Coulomb who gave his name to the electrostatic force between two charged objects. To use this explosion as a way of imaging the molecule, all of the fragment ions created must be detected and their momentum measured, from which the original geometry of the molecule is determined by working backward.

Femtosecond laser induced Nano particle production

Nano particle production and characterisation is now one of the hot topics in science, engineering and industry. Perhaps surprisingly (given its ability to disrupt matter by rapidly removing many electrons from anything in its way) femtosecond laser pulses have recently been shown to be a highly promising tool in generating nano particles. In fact it is precisely this disruptive capability which is the quality which promotes the nano particle production. When femtosecond laser pulses interact either with a liquid or a solid they cause a the material to be rapidly reduced to ionised atomic and molecular fragments which can then self organise to form either nano scale surface features which dramatically modify the properties of a material or nano particles of varying sizes and properties. One of the nicest particles is a polyyne chain which consists of carbons bound to each other and capped at each end by a hydrogen atom. These chains have been found to have extraordinary properties such as strength beyond that of diamond (also made of carbon).

Usually polyynes are produced from graphite powder (soot) in a liquid heated by an electric discharge or high energy laser pulse. Recently it has been found that instead of this messy method it is possible to take a clean solvent solution and irradiate it with pulses from a femtosecond laser. The result is a solution containing polyynes and other fragments of the initial solvent. One of the ways that the femtosecond laser is able to process the liquid effectively is by generating a bright filament, in which nonlinear interactions between the laser field and the liquid increase the length of the focus by orders of magnitude.

Dr. Sanderson has been named a Science Teaching Fellow at the University of Waterloo. Teaching Fellows work together to provide leadership and support for faculty members with the ultimate goal of improving the depth, effectiveness, and efficiency of student learning.

Read more about Dr. Sanderson;s unique approach to teaching: Student Interaction: Joseph Sanderson’s Group-Based Learning

• PHYS 111, Physics 1

Generation of polyyne and methylpolyyne molecules from toluene by intense femtosecond laser pulse irradiation
A Ramadhan, M Wesolowski, T Wakabayashi, H Shiromaru, T Fujino, ...
Journal of Physics: Conference Series 635 (11), 112125 2015

Formation of hydrocarbon species and carbon clusters through femtosecond laser ablation of cryogenic solidified methane
R Karimi, A Zaidi, Y Cai, M Hajialamdari, J Sanderson, W Duley
Journal of Physics: Conference Series. Vol. 635. No. 10. IOP Publishing, 2015

Tabletop imaging using 266 nm femtosecond laser pulses, for characterization of structural evolution in, single molecule, chemical reactions
H Ibrahim, B Wales, S Beaulieu, BE Schmidt, N Thiré, É Bisson.
Journal of Physics: Conference Series. Vol. 635. No. 11. IOP Publishing, 2015

Tabletop Imaging of Structural evolutions in Chemical Reactions
H Ibrahim, B Wales, S Beaulieu, BE Schmidt, N Thiré, EP Fowe, É Bisson.
Ultrafast Phenomena XIX. Springer International Publishing, 2015. 130-133. 

Dissociative ionization dynamics of triatomic molecules induced by soft X-rays
Ali Ramadhan, Benji Wales, Isabelle Gauthier, Mike MacDonald, Lucia Zuin, Joe Sanderson
Journal of Physics: Conference Series 635 (2015) 112137

Please see Dr. Sanderson's research website for a complete listing of his publications. 

• 2009, JSPS Fellowship
• 2003, Premiers research Excellence Award Senior

• Faculty, Centre for Advanced Materials Joining
• Principal Investigator, Nano and Micro Systems Lab

• 2012 - 2013: Making Groups Work for Large Classes and Assessing Their Impact​

1991 PhD Physics, University College, London, UK

1986 BSc Physics & Astronomy, University College, London, UK