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Q: Quantenoptik und Photonik

Q 72: Poster Laserspektroskopie

Q 72.4: Poster

Donnerstag, 16. März 2006, 16:30–18:30, Labsaal

Coherent suppression of power broadening, applied to trace detection of molecular isobars — •Lukas Brandt, Alvaro Peralta Conde, and Thomas Halfmann — TU Kaiserslautern, FB Physik, Erwin-Schrödinger-Strasse, 67663 Kaiserslautern

Trace detection of atomic or molecular species by resonantly enhanced multi-photon ionization (REMPI) exhibits a well-established tool, providing high efficiencies and selectivities in analytical applications. However, while the efficiency of trace detection increases with the driving laser intensities, power broadening reduces the spectral resolution. We present a coherent variant of REMPI, which permits suppression of power broadening. The technique is based on coherent population return (CPR), i.e. population is driven by a coherent radiation field from a ground to an excited state and back again. Power broadening does not occur, if the population in the upper state is monitored after the excitation process [1, 2]. Thus, if the ionization and excitation laser are delayed in a REMPI experiment, no power broadening limits the spectral resolution - no matter how strongly the transitions are driven. We demonstrate trace detection by REMPI, assisted by CPR, to monitor isobars of NO-molecules. We show, that irrespective of the driving laser intensity, high selectivity is maintained even if a transition is driven strongly in saturation.

[1] N.V. Vitanov, B.W.Shore, L.P.Yatsenko, K. Böhmer, T. Halfmann, T. Rickes, K. Bergmann, Opt. Comm. 199, 117 (2001)

[2] T. Halfmann, T. Rickes, N.V. Vitanov, K. Bergmann, Opt. Comm. 220, 353 (2003)