Formation of an intense pulsed beam of CH₃Cl in the |111〉 state using a 2-m electrostatic hexapole field

An intense pulsed beam of CH₃Cl in the )|111〉 state without velocity selection was focused using a 2-m electrostatic hexapole field. The beam intensity was estimated to be ∼1×10¹³ molecules pulse^-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 mrad. The improvements in beam intensity and in the divergence of the beam can be mainly ascribable to the efficient pumping of the hexapole field through the cylindrical electrodes, which enables us to employ the helium seeding to have the fast stream velocity, the narrow distribution of velocity, and the aerodynamic effects. Those factors altogether made the velocity selection of the beam unnecessary.