Two novel techniques enabling diverse probes of the chemistry of the atmospheres of outer planets are being developed in our laboratories. The study of spin-polarized hydrogen atoms which result from photodissociation of molecules offers a powerful new means of unraveling complex photochemical processes in polyatomic molecules.  Examination of the detailed speed-dependent H-atom spin polarization is achieved by determining the projection of the electron spin onto the probe laser direction. In doing so, its angular distribution, complex dissociation pathways, and coherent excitation mechanisms may be revealed.  Here we have adapted the H atom Rydberg tagging technique with its extraordinary velocity resolution to give the velocity-dependent H atom spin polarization. The methodology described herein serves as a general probe of multi-surface nonadiabatic dynamics, sensitive to coherent effects in dissociation along multiple paths, and is applicable to a wide range of astrochemically-relevant polyatomic systems. A second approach, Chirped-pulse Fourier-Transform Millimeter Wave Spectroscopy, has revolutionized broadband rotational spectroscopy with vastly reduced acquisition times, with further sensitivity possible when more molecules can interact with the microwave field. We hae developed a high-power mmWave system that incorporates a pulsed Laval flow to produce a uniform supersonic flow, yielding thermalized reactants at a high density and high volume yet low rotational temperature. It thus provides the ideal extension of the CP-FTMW technique for studying chemical reactions.  This combination promises a method of near universal application that quantitatively detects nascent product isomers and conformers with vibrational level specificity. This will be suitable for a wide range of applications in reaction dynamics studies, including combustion-, atmospheric-, and astrochemistry.

Novel experimental approaches for fundamental studies of laboratory astrochemistry

246th National Meeting (2013)

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