1P31
Oxidation reaction dynamics of gas-phase aluminum atom
(Univ. of Hyogo) HIRATA Daiki, HONMA Kenji
Oxidation reactions of metal atoms are important in atmospheric chemistry. In our laboratory,
several metal atoms have been studied with respect to their oxidation reactions. In this presentation,
we would like to present the crossed-beam study of the aluminum atom reaction with CO2. Oxidation
reactions of the aluminum atom have been studied by various techniques, because the oxidation of
aluminum is generally highly exothermic and relevant to the rocket propellant. We have carried out to
elucidate the reaction dynamics of aluminum with oxygen with resonance-enhanced multiphoton
ionization (REMPI) - velocity mapping imaging (VMI) technique [1]. Here we studied the Lewis
oxidation reaction of aluminum by carbon dioxide (R1) by using the same technique.
Al (2P) + CO2 (X1Σ+g) → AlO (X2Σ+) + CO (X1Σ+)
ΔrH00 =
17.65 kJ/mol
(R1)
The crossed-beam apparatus consists of a time-of-flight mass spectrometer with a two-dimensional
detector. Aluminum atoms were generated by laser vaporization, and were issued as an atomic beam
by carrier gas flow expanded through a pulsed nozzle. As a carrier gas, we used helium in higher
collision energy condition (45.7 kJ/mol) or nitrogen in lower collision energy condition (25.3 kJ/mol).
A CO2 molecular beam was delivered from another pulse nozzle and crossed with an Al beam at right
angle. A (1+1) REMPI via the D2Σ+-X2Σ+ transition of AlO, around 250 nm, was applied to ionize the
product vib-rotational state selectively. The mass
selected AlO+ ion was detected by a detector (MCP Phospher Screen - CCD camera) as a 2D image.
Since the AlO+ images contained “non-reaction
origin” signals, they were determined separately and
subtracted. The images were converted to kinetic energy
and angular distributions. Fig. 1 summarized kinetic
energy distributions for AlO (v = 0, J = 14) in two
collision
energies.
Fig.
2
summarized
angular
Fig. 1 Kinetic energy distributions
distributions for the same vib-rotational state. In the
higher
energy,
the
distribution
showed
a
forward-backward symmetry, however forward peak
was more pronounced at the low collision energy.
Taking into account the energetics, most of available
energy appears as the kinetic energy, and the internal
motion of CO takes almost no energy. This result
suggests the occurrence of a direct mechanism, which is
not consistent with the forward-backward symmetry. We
would like to discuss about any possible mechanisms.
Fig. 2 Center-of-mass angular distributions
[1] Honma, K.; Miyashita, K.; Matsumoto, Y. J. Chem. Phys. 2014, 140, 214304.