Detection of vibrationally excited hyroxyl radicals by absorption of the DFB diode laser radiation at the transition (ν = 3) ← (ν = 1)

[Display omitted] •Time-resolved detection of OH(v = 1) by infrared absorption in overtone region.•Vibrational relaxation of hydroxyl radical.•The yields of excited OH in the O(1D) + H2O reaction. Using a DFB laser diode at 1509.3 nm the OH(v = 1) formed in the reaction O(1D) + H2O was detected by absorption at the transition (v = 3)←(v = 1). The advantage of the method is the ability to obtain reliable data on absolute concentrations of vibrationally excited radicals. The spectrum of transient absorption near Q(3/2) line of 2Π3/2 term was recorded. At a pressure of 8 Torr He, the rotation distribution was found to be in thermal equilibrium. The yields of OH(v = 1) and OH(v = 2) in the chemical reaction were determined. The rate constants of vibrational relaxation of OH(v = 1) on H2O and SF6 were measured.