Doppler-Free Spectrum of the Barium ¹S₀⁻¹P₁ Transition by Degenerate Four-Wave Mixing Using an Air/Acetylene Flame

Abstract

Doppler-free flame spectrometry based on resonant degenerate four-wave mixing (D4WM) is shown to be an effective analytical tool for the determination of barium at high spectral resolution. Optical phase conjugation is produced in an air/acetylene flame, resulting in an optical signal that is a coherent time-reversed replica of the probe beam. The degenerate four-wave mixing spectrum of barium for the 6 s21 S0-6 s6 p1 P1 transition at 18,060.19 cm−1 is collected with a linewidth of 0.08 cm−1 (FWHM) with the use of a convenient continuously flowing atmospheric-pressure flame atomizer. A preliminary detection limit of 5 μg/mL barium, while a Doppler-free linewidth is maintained at 0.08 cm−1, is reported.

Trace Analysis of Rubidium Hyperfine Structure in a Flame Atomizer Using Sub-Doppler Laser Wave-Mixing Spectroscopy

“…It is an unusually sensitive nonlinear laser method with a relatively easy multi-wave optical setup that is suitable for trace-concentration chemical analysis. 4,5 Since the signal is inherently sub-Doppler, resonant laser wave m ixing offers excellent spectral resolution that is suitable for isotope and hyper ne structure measurements 6,7 and many other applications, including atomic frequency locking. 8 Taking advantage of both excellent spectral resolution and detection sensitivity, one could employ this relatively simple nonlinear laser m ethod for trace-concentration elemental analysis 9 and for parts-pertrillion-level m easurement of isotope and hyper ne structures.…”

Circular Dichroism Spectroscopy by Four-Wave Mixing Using Polarization Grating-Induced Thermal Gratings

“…Four-wave mixing has proven to be a powerful tool for probing the chemical and physical properties of numerous different sample types. A particularly useful technique is degenerate four-wave mixing (DFWM) which has been demonstrated as a sensitive analytical spectroscopic method in many different environments, including low-pressure hollow-cathode discharge cells, − flame atomizers, − and liquid flow cells. , In the gas phase, sub-Doppler spectral resolution allows hyperfine structure measurement and stable isotope ratio analysis at trace concentration levels . For condensed-phase analytes, attomole-level detection sensitivity has been obtained using continuously flowing liquid cells .…”