The kinetics of the reaction of hydroxyl radical (OH) with dimethyl methylphosphonate (DMMP, (CH₃O)₂CH₃PO) (reaction 1) OH + DMMP → products (1) was studied at the bath gas (He) pressure of 1 bar over the 295–837 K temperature range. Hydroxyl radicals were produced in the fast reaction of electronically excited oxygen atoms O(¹D) with H₂O. The time-resolved kinetic profiles of hydroxyl radicals were recorded via UV absorption at around 308 nm using a DC discharge H₂O/Ar lamp. The reaction rate constant exhibits a pronounced V-shaped temperature dependence, negative in the low temperature range, 295–530 K (the rate constant decreases with temperature), and positive in the elevated temperature range, 530–837 K (the rate constant increases with temperature), with a turning point at 530 ± 10 K. The rate constant could not be adequately fitted with a standard 3-parameter modified Arrhenius expression. The data were fitted with a 5-parameter expression as: k₁ = 2.19 × 10⁻¹⁴(T/298)^2.43exp(15.02 kJ mol⁻¹/RT) + 1.71 × 10⁻¹⁰exp(−26.51 kJ mol⁻¹/RT) cm³molecule⁻¹s⁻¹ (295–837 K). In addition, a theoretically predicted pressure dependence for such reactions was experimentally observed for the first time.

Vibrationally excited OH radicals produced in the O(1D) + CH4 reaction were studied using direct infrared absorption spectroscopy. The formation and decay kinetics of OH in vibrational v = 0 3 states were measured, and population inversion was observed at the initial moment of the reaction. Concentrations of OH in different vibrational states were determined from the absorption signals, and state-resolved formation probabilities were obtained from extrapolated kinetic curves. The resulting vibrational distribution, P(v=0) : P(v=1) : P(v=2) : P(v=3) : P(v=4) = 0.10:0.24:0.33:0.31:0.02, agrees with the previous studies but indicates a significantly higher yield of OH(v=3).

The kinetics of vibrationally excited OH(ν = 1) and OH(ν = 2) radicals was studied by time-resolved laser absorption in the overtone IR region. Two DFB laser diodes, 1509.3 and 1589 nm, were used. The technique allowed for the reliable study of the vibrational relaxation kinetics as well as the relative populations of the vibrationally excited states. The yields of OH(ν = 1) and OH(ν = 2) in the reaction O(¹D) + H₂O were determined. The rate constant of OH(ν = 1) relaxation in collision with water molecules was obtained ((9.2 ± 2.0) × 10⁻¹² cm³/s). The dynamics of OH(ν = 1) and OH(ν = 2) populations were analyzed in detail, which made it possible to separately determine the relative contribution of the vibrational ladder relaxation channels OH(ν = 2) → OH(ν = 1) → OH(ν = 0) and the direct relaxation OH(ν = 2) → OH(ν = 0).

Infrared multiphoton dissociation of Ge(OCH₃)₄ molecules by irradiation with a pulsed TEA CO₂ laser has been studied. The basic characteristics of the process have been experimentally investigated. The spectral characterization of the dissociation has been made. The product composition of the dissociation has been analyzed, and possible dissociation pathways have been proposed.