Berlin 2005 – wissenschaftliches Programm
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Q: Quantenoptik und Photonik
Q 68: Laserspektroskopie II
Q 68.1: Vortrag
Mittwoch, 9. März 2005, 11:00–11:15, HU 2014a
Ultrasensitive NICE-OHMS Detection of Molecular Oxygen at Cryogenic Temperatures — •Dennis Weise1 and Achim Peters2 — 1Universität Konstanz — 2Humboldt-Universität zu Berlin
Dilute samples of cold or ultracold molecules with special properties are appealing systems for precision studies towards the establishment of new frequency standards or tests of fundamental principles in physics, such as the symmetrization postulate or CP violation. However, suitable transitions are usually quite weak and attainable number densities inherently low, so that extremely high sensitivity is required for spectroscopy. This is provided in the NICE-OHMS scheme (Noise-Immune Cavity-Enhanced Optical Heterodyne Molecular Spectroscopy) by combining the respective benefits of cavity-enhanced and lock-in detection.
In the work presented here, NICE-OHMS has for the first time been implemented in a cryogenic environment, which serves to cool the species of interests to liquid nitrogen or liquid helium temperatures. Introduction from room-temperature into the cryogenic cell is accomplished via capillary injection. Using a scanned linear resonator with a finesse of ∼ 90 000 and a length of 86 mm, several lines in the R branch spectrum of the atmospheric A band of molecular oxygen have been recorded at 77 K. An integrated detection sensitivity of 8.8 × 10−9/√Hz is achieved, corresponding to a minimum detectable absorption coefficient of 1.02 × 10−8/cm at 10 ms integration time. It is limited by etalon effects from windows and rf interferences at the modulation frequency of 1.734 GHz.