Topics And Instrumentation In Chemical Reaction Dynamics
The relative reactivity of methane excited in the antisymmetric stretching mode (?3) vs. the ground state in a prototype metal-insertion reaction, Y + CH4 ? YCH2 + H2, has been measured in crossed molecular beam scattering. Under isoenergetic conditions where the sum of available vibrational and translational energy is held constant, the vibrationally excited state is at least 2.2 times more reactive than the ground state. The mid-infrared light source used to excite the methane is an Nd:YAGpumped pulsed optical parametric oscillator/amplifier seeded with a continuous wave laser diode in the near infrared. The OPO/OPA system has an overall quantum efficiency of greater than 0.25 when using 350 mJ/pulse of pump light. The light source also includes a self-drilled vacuum spatial filter for the pump beam, enabling it to be used with pump lasers exhibiting structured beam profiles. Also presented are new piezo-electric bimorph actuators for use in high-speed pulsed valves used to generate pulsed molecular beams. They are more resistant to chemical attack than their commercial counterparts and deliver shorter pulses. The short pulse duration can provide greater beam intensities for a given pumping speed or reduce the pumping speed required to generate a given beam intensity.
Chemical Reaction Dynamics
dissertation or thesis