A new spectroscopic technique for studying electronically excited molecules at very high angular momentum has been developed and tested by scientists in Canada.
The team, from the University of British Columbia, headed by Valery Milner, have used an optical centrifuge to excite oxygen to rotational states that otherwise can’t be reached. An optical centrifuge combines two laser pulses to create an intense electric field which undergoes angular acceleration to drive molecules into the remarkable angular momentum states. The super rotation state reached for oxygen in the study is equivalent to heating the molecule to 50,000K, a temperature that is too hot for the molecule to survive. A spectroscopic technique called resonance-enhanced multi-photon ionisation was combined with the centrifuge and by carefully controlling and calibrating the rotational speed of the centrifuge a spectrum can be viewed as a two-dimensional function of photon energy and angular momentum.
‘It greatly simplifies the spectra,’ says Aleksey Korobenko, the lead scientist on this study. ‘Even when the photon energy branches are overlapping, you can track one by one the rotational peaks which you can’t otherwise separate out.’
Interested to know more?
Read the article in PCCP:
Rotational spectroscopy with an optical centrifuge
Aleksey Korobenko, Alexander A. Milner, John W. Hepburn and Valery Milner
Phys. Chem. Chem. Phys., 2014, Advance Article
DOI: 10.1039/C3CP54598A, Paper