Open AccessTwo-photon-excited fluorescence of CO: experiments and modeling
Author(s) -
Maria Ruchkina,
Pengji Ding,
Marcus Aldén,
Joakim Bood,
Christian Brackmann
Publication year - 2019
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.27.025656
Subject(s) - femtosecond , laser , optics , materials science , laser induced fluorescence , photoionization , fluorescence , laser linewidth , ultrafast laser spectroscopy , excited state , atomic physics , physics , ionization , ion , quantum mechanics
A model based on rate-equation analysis has been developed for simulation of two-photon-excited laser-induced fluorescence of carbon monoxide (CO) in the Hopfield-Birge band at 230 nm. The model has been compared with experimental fluorescence profiles measured along focused beams provided by lasers emitting nano-, pico-, and femtosecond pulses. Good quantitative agreement was obtained between simulations and experimental data obtained in premixed CH 4 /C 2 H 4 -air flames. For excitation with femtosecond pulses, experimental and simulated fluorescence signals showed quadratic dependence on laser power under conditions of low laser irradiance, whereas different sublinear dependencies were obtained at higher irradiances due to photoionization. Simulations of CO signal versus femtosecond laser linewidth suggest the strongest signal for a transform-limited pulse, which is sufficiently broad spectrally to cover the CO Q-branch absorption spectrum. Altogether, the developed rate-equation model allows for analysis of two-photon excitation fluorescence to arrange suitable diagnostic configurations and retrieve quantitative data for CO as well as other species in combustion, such as atomic oxygen and hydrogen.