A PULSED-LEAK VALVE FOR USE WITH ION TRAPPING MASS SPECTROMETERS

A pulsed-leak valve that allows the introduction of a prolonged, flat, and controllable pulse of gas is described. Test results from the val ve that utilized a Fourier transform ion cyclotron resonance mass spec trometer with Ar and C2H6 as the sample gases indicate that the valve functions as expected and yields basically rectangular pressure profil es in the cell region. The rise and fall times are similar to those of just the stand-alone pulsed valve and are believed to be determined m ainly by the design of the vacuum system, rather than the design of th e pulsed-leak valve. Kinetic data for the reaction of Nb+ with C2H6, a cquired with the use of the pulsed-leak valve to introduce the C2H6 ga s, demonstrates the practical application of this valve for kinetic an d other analogous studies. Use of the pulsed-leak valve greatly reduce s the loss of the reactant ion signal during the cooling period.