Novel technique sheds new light on global warming and ozone depletion
Andor iKon-M camera at the heart of novel TPEPICO (threshold photoelectron–photoion coincidence) velocity imaging apparatus
Andor iKon-M camera at the heart of novel TPEPICO velocity imaging apparatus
02 October, 2012
Belfast, 02 October, 2012.
Despite its low atmospheric concentration and comical connections, nitrous oxide is no laughing matter. It is the fourth largest
contributor to global warming, behind water vapour, carbon dioxide and methane, and has replaced CFCs as the dominant
ozone-depleting substance emitted by humans – a situation that is unlikely to change throughout the 21st Century.
Stratospheric ozone is regulated by nitric oxide, formed when nitrous oxide reacts with oxygen atoms. However, even though
extensive experimental studies into this reaction have been conducted, the photodissociation mechanism of nitrous oxide,
the kinetic energy and internal state distributions of fragments, and the angular distributions of fragment ions are still unclear.
Now, a team working at China’s National Synchrotron Radiation Laboratory at Hefei has used a novel threshold photoelectron–photoion
coincidence (TPEPICO) velocity imaging technique to determine the formation pathways of nitric oxide. The corresponding vibrational
state distributions of NO+ have also been identified for every dissociation channel.
“Ultra low noise performance is vital in our work on the photodissociation dynamics of ions,” says one of the lead researchers,
Xiaoguo Zhou. “At the heart of the experimental apparatus is Andor’s thermoelectrically cooled iKon-M 934 camera. Compared to
cameras normally used in ion imaging experiments, the Andor camera offered very much lower read noise and high sensitivity over
accumulation periods of up to 60 minutes. We also used the Andor Solis software supplied with the camera to process the images.
For instance, we would often need to subtract the background and Solis processed the images easily and quickly.”
The TPEPICO apparatus was set up at the synchrotron’s U14-A beam line and a continuous supersonic molecular beam of pure N2O gas
introduced into the photoionization region through a homemade 30 micron diameter nozzle. Photoelectrons and photoions were
collected through a special ion lens to map their velocity images simultaneously and the coincident photoions projected onto
a dual microchannel plate backed by a phosphor screen where the Andor DU934N-BV TE-cooled CCD detector recorded the images.
By applying a pulsed high voltage on MCP as the mass gate, the three-dimensional (3D) time-sliced image of ions was obtained.
Andor’s iKon-M 934 series cameras are designed to offer the ultimate in high sensitivity, low noise performance, which makes
them ideal for demanding imaging applications. Boasting up to 95% QEmax, high dynamic range, 13μm pixels and exceptionally low
readout noise, these high resolution CCD cameras benefit from negligible dark current with industry-leading thermoelectric
cooling down to -100°C.
Andor is represent in Israel by New Technology SK (Newtech):
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