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Reaction Dynamics in Extreme Environments - Boron Reactions
Ralf I. Kaiser, University of Hawaii at Manoa (FA9550-09-1-0177 )
Reaction Dynamics
Results
We have elucidated the energetics and dynamics of elementary
reactions of ground state boron atoms (B(2Pj)) with simple
nitrogen-bearing molecules: ammonia (NH3) and hydrogen cyanide
(HCN). The closed shell molecules serve as prototype reaction
partners to access the HxBCyN (x=0,1,2,3; y=0,1) potential energy
surface which is important in the fields of basic physical chemistry (reaction dynamics), combustion chemistry, material sciences,
chemical propulsion systems, physical organic chemistry, and chemical vapor deposition processes (boron-nitride films, ternary BCN
compounds). The experiments are pooled together with electronic
structure calculations (Bartlett et al.; Mebel et al.) to verify the elucidated reaction mechanisms theoretically; this ultimately bridges
the understanding of reactive scattering processes involving small
boron-bearing systems via quantum chemical methods and experiments.
The reaction of boron with hydrogen cyanide revealed that the
boronisocyanide molecule, [BNC], is formed as the exclusive product under gas phase single collision conditions via indirect scattering dynamics. The corresponding TOF spectra of the ionized
parent molecule are depicted on the right. We also show that higher
energy isomers such as the hitherto unnoticed, ring-strained cyclic
BNC structure, which is isoelectronic to the triplet, cyclic tricarbon
molecule, [C3], exist as local minima. Our study presents the first
clean synthesis and observation of gas phase boronisocyanide
providing a door way for further fundamental, spectroscopic studies on one of the simplest triatomic molecules composed solely of
group III – V elements. The data from our studies also help to
understand the chemical synthesis of macroscopic amounts of BNC
material on the industrial scale.
HNBH
B. Jones et al., J. Phys. Chem. A 2010,
114, 8999–9006
F. Zhang et al., J. Phys. Chem. A, DOI:
10.1021/jp107210d
Reaction Dynamics in Extreme Environments - Polymers
Ralf I. Kaiser, University of Hawaii at Manoa (FA9550-09-1-0177 )
Reaction Dynamics
This project investigates the effects of ionizing radiation with polymers (Kapton, Teflon, PE, PS, PMMA) utilizing a surface scattering
machine. These experiments help to untangle the stability of polymers toward space weathering (cosmic rays, energetic electrons, ions,
photons) at temperatures ranging from 10 K to 300 K to mimic the extreme conditions experienced in Low Earth Orbit and the surfaces
of the moon and Mars. Here, we report on the interaction of energetic electrons as generated in the track of galactic cosmic ray particles
with all five polymers in a UHV chamber (510-11 torr). The irradiated samples are analyzed via infrared and UVVIS spectroscopy; the
gas phase is monitored via a quadrupole mass spectrometer. Mechanistical results on polymer degradation via chain rupture versus
chain branching, molecular hydrogen, carbon monoxide, and carbon dioxide formation are discussed. Kinetic profiles of the newly
formed molecular bonds are also presented. Successive experiments, done in collaboration with the Sibener Group in Chicago, will
focus on the effects of singly ionized oxygen atoms with spin-coated polymer films (100 – 200 nm) in collaboration with Sibener et al..
C.P. Ennis & R.I. Kaiser
Phys. Chem. Chem. Phys.,
2010, 12,14884-14915