Scientists at the Ruhr-Universität Bochum in
Germany have performed high-precision, ultracold chemical studies of
nitrogen oxide (NO) molecules by inserting them into droplets of
liquid helium (see figure).
Science magazine's "molecule of the year" for 1992, is important
because of its role in atmospheric chemistry and in signal
transduction in biology. A radical is a molecular entity
(sometimes charged and sometimes neutral) which enters into chemical
reactions as a unit. To sharpen our understanding of this important
molecule and its reactions, it would be desirable to cool it down,
the better to observe its complex spectra of quantum levels
corresponding to various vibrational and rotational states.
new experiment, liquid helium is shot from a cold nozzle into
vacuum. The resultant balls, each containing about 3,000 atoms, are
allowed to fall into a pipe where NO molecules are lurking. The NO
is totally enveloped and, within its superfluid-helium cocoon at a
temperature of about 0.4 Kelvin, it spins freely. The helium acts
provides a cold environment but does not interact chemically with
the NO molecules. Because of this a high-resolution infrared
spectrum of NO in fluids could be recorded for the first time.
has been observed before in the gas phase, but never before has such
a high resolution spectrum be seen in the helium environment.
Haeften et al.,
Physical Review Letters, 18 November 2005
Contact Martina Havenith,
The Havenith lab's Web site