CRASY for CS2: Mass-selective rotational spectra, referenced to a clock.

Abstract

Mass-correlated rotational alignment spectroscopy (mass-CRASY) is a laser spectroscopic method based on the optical excitation and probing of rotational coherences in a mass spectrometer [1]. The presented work extended CRASY by referencing the spectroscopic data via a stable laser oscillator frequency to an external clock. The experiment therefore provides a first time-domain equivalent to frequency comb spectroscopy (2005 Nobel price in Physics). Data for carbon disulfide shows the inherent capabilities of this novel spectroscopic method: The rotational constant for the main isotopologue was resolved with sub-kHz resolution and accuracy (equivalent to a relative accuracy of 2.1·10-7). Other naturally occurring isotopologues were characterized in the same experiment with relative uncertainties in the low kHz regime. The talk will present the measurement concept and the technological requirements for high-accuracy measurements in the time domain. It will also highlight the scientific problems that require correlated measurements to facilitate signal assignment in heterogeneous samples.