High-temperature rotational-vibrational O2CO2 coherent Raman spectroscopy with ultrabroadband femtosecond laser excitation generated in-situ

We present ultrabroadband two-beam femtosecond/picosecond coherent Raman spectroscopy on the ro-vibrational spectra of CO2 and O2, applied for multispecies thermometry relative concentration measurements in a standard laminar premixed hydrocarbon flame. The experimental system employs fs-laser-induced filamentation to generate compressed supercontinuum in-situ, resulting ∼24 fs full-width-at-half-maximum pump/Stokes pulse with sufficient bandwidth excite all transitions up 1600 cm-1. report simultaneous recording Q-branch O2 O-, Q- S-branch Stokes (CSRS) basis single-laser-shot. use as generation mechanism has advantage greatly simplifying setup, it avoids hollow-core fibres chirped mirrors deliver near-transform-limited at measurement location. Time-domain models spectrum were developed. modelling accounts 180 vibrational bands their interaction Fermi polyads, is based recently available, comprehensive calculations transition dipole moments molecule: availability spectroscopic data these many crucial model high-temperature acquired flue gases flames, where temperature can exceed 2000 K. numerical code was employed evaluate CSRS products methane/air flame provided Bunsen burner, varying equivalence ratio range 0.6–1.05. performance spectral assessed by extracting temperatures from 40-laser-shots averaged spectra, accuracy precision ∼5% ∼1%, respectively, high 2220