FORMATION OF AN INTENSE PULSED-BEAM OF CH3CL IN THE [111] STATE USINGA 2-M ELECTROSTATIC HEXAPOLE FIELD

An intense pulsed beam of CH3Cl in the \111] state without velocity se lection was focused using a 2-m electrostatic hexapole field. The beam intensity was estimated to be approximately 1 X 10(13) molecules puls e-1, which is much greater than the similar beams in the earlier study of Gandhi et al. by at least two orders of magnitude. The beam had a 3-ms pulse width and was focused with an angular divergence of 0.7 mra d. The improvements in beam intensity and in the divergence of the bea m can be mainly ascribable to the efficient pumping of the hexapole fi eld through the cylindrical electrodes, which enables us to employ the helium seeding to have the fast stream velocity, the narrow distribut ion of velocity, and the aerodynamic effects. Those factors altogether made the velocity selection of the beam unnecessary.