Two-line laser-induced fluorescence imaging of vibrational temperatures in a NO-seeded flame

Two-dimensional temperature fields are measured in lean and sooting flames by means of two-color laser-induced fluorescence (LIF) imaging that uses seeded NO. Vibrational thermometry is performed by the probing of different vibrational ground-state levels. Spectral properties of the excited transitions within the A (2)Sigma (+)-X (2)Pi system are well known from previous studies. The energy difference of 1974 cm(-1) between the (0,0)Q(1) + P-21(33.5) and the (0,2)O-12(5.5) lines offers great sensitivity in the temperature range that is relevant for combustion processes. Excitation is possible by use of a tunable KrF excimer laser on its fundamental (248-nm) and Raman shifted (in H-2, 225-nm) wavelengths. An excitation scheme for instantaneous two-line measurements by use of a single laser is developed. The possibility of single-shot measurements is discussed. (C) 2001 Optical Society of America OCIS codes: 280.1740, 300.2530, 140.2180, 300.6360, 120.6780.