The Detection of Crystal Field Splitting in Eu(III) with a Narrow-band Tunable Cw Dye Laser

Abstract

The development of lasers which can be tuned over a wide range, typically 50-100nm, with the output wavelength confined to a narrow-band has made it possible to increase both the sensitivity and resolution of conventional spectroscopy. The strong signal generated by lasers in comparison to the usual broad-band incandescent or line emission excitation source vastly improves the signal to noise ratio, permitting the observation of relatively weak absorptions which might otherwise be masked by thermal noise. This allows both the viewing of spectral lines with high absorptivity at low concentration or low absorptivity lines without undue concentration. Because the laser output can be confined to a bandwidth much narrower than the resolution of the best commercial instruments, the ultimate resolution of spectral lines is governed not by the instrumental width of spectroscopic instruments but by the natural width of molecular transitions. This experiment, the firs of its kind to be performed at Argonne National Laboratory, utilized just such a tunable laser operating in a narrow band to detect crystal field splitting in a very weak absorption band of trivalent europium in solution. The transition studied was 7F1 -- 5Do. This level, which has a molar extinction coefficient (E) in the range of o.01-0.02, is triply degenerate.