Cooling of large molecules below 1 K and He clusters formation

We present here the design details of a high-pressure pulsed valve that generates intense supersonic jets. The measured rotational contours of Aniline indicate that temperatures lower than 0.5 K can be achieved before the formation of clusters with the He carrier gas. The spectral shifts and vibronic structure of Anthracene-He-n clusters (n=1-6) are showing some surprising features. (C) 2000 American Institute of Physics. [S0021-9606(00)01117-X].