INSTALLATION FOR GENERATING MOLECULAR CLUSTERS IN A PULSED SUPERSONICBEAM

An installation for generating and recording pulsed beams of molecular clusters is described. The installation contains a pulsed supersonic nozzle, a molecular-beam generation system, and a pulsed-beam detector . The detector is an MS 7303 quadrupole mass-spectrometer and a vacuum system. The measurement hardware contains an IBM PC/AT 286 and CAMAC crate and is used to record and to control the experiment. The range o f operating pressures in the beam source chamber is 10(-5) torr-5 atm; the duration of the nozzle's open state ranges from 300 musec to 1 ms ec; and the pulse frequency is 1-20 Hz. The beam parameters were evalu ated by a numerical simulation of the gas-carrier's beam shape which g ives a Mach number of M congruent-to 3, a beam temperature of congruen t-to 65-degrees-K, and a beam source pressure of 500 torr. The lines o btained from the mass spectrum of the beams showed a mixture of size c lusters. The line identification procedure is based on a profile analy sis of the gas pulse. Clusters of formic acid, alcohol, methyl iodide, sulphur dioxide, benzene, etc. and containing up to twelve molecules were obtained and identified on the installation.