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High signal-to-noise ratio laser technique for accurate measurements of spectral line parameters



A. Cygan, D Lisak, S. Wojtewicz, J. Domyslawska, Joseph T. Hodges, R.S. Trawinski, R. Ciurylo


We present a new cavity-enhanced technique for the precise measurement of absorption line shape and line position. This approach, which combines high-bandwidth locking of a continuous wave probe laser with frequency-stabilized cavity ring-down spectroscopy, enables long-term signal averaging and yields high-resolution spectra with a relatively wide dynamic range and low detection limit. By probing rovibronic transitions of the oxygen B-band near a wavelength of 689 nm, we demonstrate exceptionally precise measurements of absorption line shape and line position. We report a signal-to-noise ratio of 220,000:1 a minimum detectable absorption coefficient of 2.4E-11/cm and line center measurement with a precision of 26 kHz. In our measurements of self-broadened oxygen spectra, careful line shape analysis revealed a subtle line shape asymmetry caused by the speed dependence of the collisional shift. The precision achieved enabled us to quantify systematic line shape deviations that were approximately 1 part in 80,000 of the peak absorption. We also discuss how this method can enable experiments that address a number of fundamental physical problems including the accurate measurement of the Boltzmann constant and tests of the symmetrization postulate.
Physical Review Letters


oxygen, line shape, speed dependence, collisional narrowing, cavity ring-down, Boltzmann constant


Cygan, A. , Lisak, D. , Wojtewicz, S. , Domyslawska, J. , Hodges, J. , Trawinski, R. and Ciurylo, R. (2012), High signal-to-noise ratio laser technique for accurate measurements of spectral line parameters, Physical Review Letters, [online],, (Accessed June 22, 2024)


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Created February 8, 2012, Updated October 12, 2021