MY AMERICAN SCIENTIST
LOG IN! REGISTER!
SEARCH
 
RSS
Logo IMG

MARGINALIA

A Really Moving Story

Roald Hoffmann

Beam Me Down

Both of the studies described above depend on supersonic molecular beams expanding into a vacuum—in Ceyer's case a beam of neon, argon or krypton seeded in helium, in Zare's case a pulsed beam source of ICl molecules. The velocities of the molecules emerging from these beams can be controlled by heating the expansion nozzle over a wide temperature range. The beams are "skimmed" downstream by sharp-edged openings and collimated by slits, obstructions and otherwise-shaped orifices. The language of handling tenuous gases is one of machined metals—walking down the lanes of exhibitor's wares at a meeting of the American Vacuum Society is a fantastic experience (in the advertisers' wares, I once found a poem). The language is one of intended control. The outcome, if everything is just right (days of alignment and pumping to get it there), is a molecular beam exquisitely well defined in its dimensions and in the speed of the molecules coursing down their appointed paths.





» Post Comment

 

EMAIL TO A FRIEND :

Of Possible Interest

Feature Article: Engineered Molecules for Smarter Medicines

Perspective: Little Interactions Mean a Lot

Spotlight: In the News

Subscribe to American Scientist