A New Method of Producing High Speed Molecular Beams

摘要

A new method of producing a pulsed, cold beam of high velocity neutral molecules is shown to be feasible. A hollow container filled with a chosen gas is mechanically accelerated to a high velocity in a rifle or light gas gun. The container (called a sabot) is subsequently opened to allow the gas to emerge. The sabot is then slowed or deflected. Velocities up to about 3 km/sec can be achieved with a Super Swift rifle and up to about 10 km/sec with a light gas gun. It appears feasible to produce a pulsed beam at 10 km/sec with an angular divergence of = 2.5 degrees and a spread in velocity of = 4%. A 5 micro sec pulse with an instantaneous intensity of the order of 2 x 10 to the 23rd power molecules/sq cm -sec can be achieved. A beam of N2 crossed with a low velocity beam of CO or CO2 produces vibrationally excited molecules in sufficient quantity to be detected with state-of-the-art techniques. It appears feasible to measure the cross sections for collisional excitation of the vibrational levels of CO2 and CO by N2, and the cross sections for the exchange of vibrational energy between N2 and CO2 or CO. The total cross section, which gives the mean free path, can also be obtained. (Author)