Degenerate four-wave mixing spectroscopy and spectral simulation of C2 in an atmospheric pressure oxy-acetylene flame

Abstract

Rotational level dependence of ground state recovery rates for OH X 2 Π(v ″ =0) in atmospheric pressure flames using the picosecond saturating-pump degenerate four-wave mixing probe technique Highly predissociative levels of the D 2 Π state of CH studied with the two-color resonant four-wave mixing technique Absolute HCO concentration measurements in methane/air flame using intracavity laser spectroscopyThe d 3 ⌸ g ↔a 3 ⌸ u Swan bands of C 2 have been recorded with high resolution using DFWM in the nearly Doppler free, phase conjugate geometry. C 2 was probed in a standard oxy-acetylene welding flame with excellent signal-to-noise ratio and spectral resolution. Theoretical spectra were simulated and fitted directly to the complex overlapping spectra. The good agreement obtained shows that DFWM holds promise to become a robust and reliable tool for flame thermometry. Current theories of DFWM are reviewed in context of the present work and advantages and disadvantages of the technique are discussed.

Laser diagnostics and minor species detection in combustion using resonant four-wave mixing

“…On the other hand destructive interference leads to dips in the intensity that appear to sharpen the resonances on some spectral features. Such features were observed in DFWM spectra of C 2 in an oxy-acetylene flame [87]. Incorporating such effects leads to better fits of theoretically modelled spectra with experimental data.…”

“…Since then many molecular and radical species have been detected in flames, cells or high temperature arc sources making use of the discrimination afforded by the coherent signal against flame luminescence or scattering. Important diatomic radical species OH, NH [82,83], CH [84], CN [85] and C 2 [86,87] were detected and used to evaluate the utility of DFWM as a diagnostic technique in flames. Stable combustion product species such as NO [88] and NO 2 [89] which are major atmospheric pollutants were also detected.…”

Deperturbation study of the state of C2 by applying degenerate and two-color resonant four-wave mixing

“…2 depicts the wavelength region of the (4, 3) band of the d 3 P g À a 3 P u system. In addition transitions appear in this range that are due to other sequence bands such as (5,4) and (6,5). The bands are denoted by the standard nomenclature ðv 0 ; v 00 Þ.…”

“…The strong d 3 P g À a 3 P u electronic system has been used to detect this minor species in combustion processes by applying numerous experimental techniques such as laser-induced fluorescence (LIF) [1][2][3], chemiluminescence [1], degenerate four-wave mixing (DFWM) [4,5], cavity ring-down (CRD) [2,6,7] and intracavity laser absorption spectroscopy (ICL) [8]. In addition, a recent experiment reports on the application of polarization spectroscopy of C 2 to visualize soot formation [9] and LIF for soot volume fraction measurements [10].…”

Degenerate four wave mixing of pyridazine from a slit nozzle

“…This enables high sensitivity detection in adverse environments such as a combustion flame. [20][21][22][23][24][25][26] Independent of the decay dynamics for the resonant excited state, DFWM and TC-LIG have attested their superiority for detecting nonfluorescing or dissociative species. [27][28][29][30][31][32][33][34][35] Recently, Wasserman et al investigated the possibility of extracting the angular momentum anisotropy of the absorbing species using DFWM.…”