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

The electronic quenching rate constants of NO A2Σ (υ′ = 0, 1), E2Σ (υ′ = 2, 3, 4) and F2Δ (υ′ = 1, 2, 3) states by gas air are reported. The experiments were carried out by measuring the total fluorescence intensity of A2Σ (υ′ = 0, 1) → X2Π (υ″) transition at various air pressures. It gives the Stern–Volmer plots. The quenching rate constants of A2Σ (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 E2Σ (υ′ = 2, 3, 4), F2Δ (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 cm3/molecule s. They are much larger than those of A2Σ (υ′) state, whose rate constants are in the order of 10−13 cm3/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 A2Σ (υ′ ≥ 2) states in existing literatures. The agreement indicates the potential use of PA spectroscopy for measuring the electronic quenching rate.

A typical PA spectrum of NO measured at room temperature and with sample gases of 226 Pa pure NO +30 × 133 Pa air. The excited states and their vibrational number are labeled. The label A(0) indicates υ′ = 0 energy level of A2Σ state and so on.Figure optionsDownload as PowerPoint slideResearch highlights
► The quenching rate constants of NO excited states are obtained by PA spectroscopy.
► The constants of E and F states are larger than the one of A state.
► The quenching rate constants increase with the vibrational energy levels.
► The potential use of PA spectroscopy for measuring quenching rate is observed.