Time-sliced ion-velocity imaging study of the reaction Y + O2→ YO + O

Abstract

The oxidation reaction dynamics of the gas-phase yttrium atoms by oxygen molecules was studied under crossed-beam conditions. The product YO was detected using a time-of-flight mass spectrometer combined with laser single-photon ionization. An acceleration lens system designed for the ion-velocity mapping conditions, a two-dimensional (2-D) detector, and a time-slicing technique were used to obtain the velocity and angular distributions of the products. Two ionization wavelengths were used for the internal (vibrational and/or electronic) energy selective detection of YO. The single photon of the shorter wavelength (202.0 nm) can ionize all states of YO(X (2)Σ, A' (2)Δ, and A (2)Π), while electronically excited YO(A' and A) are dominantly ionized at a longer wavelength (285.0 nm). Time-sliced images were converted to the velocity and angular distributions in the center-of-mass frame. The general features of the velocity distributions of YO, determined at two wavelengths, were well represented by those expected from the statistical energy disposal model. The forward-backward symmetry was also observed for two images. These results suggest that the reaction proceeds via long-lived intermediates, and that this mechanism is consistent with previous chemiluminescence/LIF studies.

Studies of bimolecular reaction dynamics using pulsed high-intensity vacuum-ultraviolet lasers for photoionization detection

“…[45][46][47][48] Honma and coworkers have recently employed imaging in reactions of transition metal atoms with oxidants such as O 2 . 113 Such reactions have large cross sections and are amenable to ionization schemes employing near-UV lasers. 113 For such cases, the molecular species of interest can be ionized selectively with high efficiency and the probability for ionization of reactant molecules or other products is very small.…”

“…113 Such reactions have large cross sections and are amenable to ionization schemes employing near-UV lasers. 113 For such cases, the molecular species of interest can be ionized selectively with high efficiency and the probability for ionization of reactant molecules or other products is very small. On the other hand, for many studies, the use of nonresonant VUV ionization coupled with ion imaging detection is likely to be complicated by photodissociation of molecules in the interaction region 45 or from bimolecular reactions of ions produced by the VUV.…”

Reaction dynamics of Mo + O2 → MoO + O studied by a crossed-beam velocity map imaging technique

“…In a previous study of the oxidation reaction of the yittrium atom, a small amount of the metastable state, Y(a 4 F), was present in the supersonic expansion, even though it has an electronic energy higher than 10 000 cm −1 (∼120 kJ/mol). 33 Two metastable states of Mo, a 5 S 2 and a 5 D J , have similar electronic energies, and may be present in the Mo beam. 39 Since the a 5 D J state is much less reactive with O 2 than the ground state, only the a 5 S 2 state should be considered.…”

“…32,33 Molybdenum atoms were generated by laser vaporization, and were issued as an atomic beam by carrier gas flow expanded through a pulsed nozzle (Jordan PSV, 1.0 mm diameter). Several carrier gases were used; the velocities of the Mo atom and the collision energies are summarized in Table I.…”