Photo-acoustic detection on electronic quenching rate constants of NO excited states.

Abstract The electronic quenching rate constants of NO A 2 Σ ( υ ′ = 0, 1), E 2 Σ (υ′ = 2, 3, 4) and F 2 Δ ( υ ′ = 1, 2, 3) states by gas air are reported. The experiments were carried out by measuring the total fluorescence intensity of A 2 Σ ( υ ′ = 0, 1) → X 2 Π ( υ ″) transition at various air pressures. It gives the Stern–Volmer plots. The quenching rate constants of A 2 Σ ( υ ′ = 0, 1) states are obtained from the slope of Stern–Volmer plots and the known radiative lifetime. Based on the primary results of the work, we have measured the quenching rate constants of high excited E 2 Σ ( υ ′ = 2, 3, 4), F 2 Δ ( υ ′ = 1, 2, 3) states for the first time with the technique of photo-acoustic (PA) spectroscopy. It is shown that the electronic quenching rate constants of NO E ( υ ′) and F ( υ ′) states are in the order of 10 −10  cm 3 /molecule s. They are much larger than those of A 2 Σ ( υ ′) state, whose rate constants are in the order of 10 −13  cm 3 /molecule s. For E ( υ ′) and F ( υ ′) states, it is also found that the quenching rate constants increase with the vibrational energy levels. Similar result has been reported also for A 2 Σ ( υ ′ ≥ 2) states in existing literatures. The agreement indicates the potential use of PA spectroscopy for measuring the electronic quenching rate.