CO A-X system for constraining cosmological drift of the proton-electron mass ratio
Oliveira, N. de
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The A(1)Pi - X-1 Sigma(+) band system of carbon monoxide, which has been detected in six highly redshifted galaxies (z = 1.6-2.7), is identified as a probe method to search for possible variations of the proton-electron mass ratio (mu) on cosmological time scales. Laboratory wavelengths of the spectral lines of the A - X (upsilon,0) bands for upsilon = 0-9 have been determined at an accuracy of Delta lambda/lambda = 1.5 x 10(-7) through VUV Fourier-transform absorption spectroscopy, providing a comprehensive and accurate zero-redshift data set. For the (0,0) and (1,0) bands, two-photon Doppler-free laser spectroscopy has been applied at the 3 x 10(-8) accuracy level, verifying the absorption data. Sensitivity coefficients K-mu for a varying mu have been calculated for the CO A - X bands so that an operational method results to search for mu variation.