Quantum Solvent

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).

NO, 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.

In the 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.

NO 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, martina.havenith@ruhr-uni-bochum.de
The Havenith lab's Web site