15min:

M. L. NIU, E. J. SALUMBIDES, D. ZHAO, J. BAGDONAITE, Department of Physics and Astronomy, and LaserLaB, VU University, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands; N. DE OLIVEIRA, D. JOYEUX, L. NAHON, Synchrotron Soleil, Orme des Merisiers, St Aubin BP 48, 91192, GIF sur Yvette cedex, France; R. W. FIELD, Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA; AND W. UBACHS, Department of Physics and Astronomy, and LaserLaB, VU University, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands.

The \textrmA¹ -\textrmX^{1 +} band system of carbon monoxide, which has been detected in six highly redshifted galaxies (z=1.6-2.7), is identified as a novel probe method to search for possible variations of the proton-electron mass ratio (µ) on cosmological time scales. Laboratory wavelengths of the spectral lines of the A-X (v,0) bands for v=0-9 have been determined at an accuracy of / =1.5 × 10^-7 through VUV Fourier-transform absorption spectroscopy, providing a comprehensive and accurate zero-redshift data set. Two-photon Doppler-free laser spectroscopy has been applied for the (0,0) and (1,0) bands, achieving 3 × 10^-8 accuracy level, verifying the absorption data. Accurate sensitivity coefficients K_µ for a varying µ have been calculated for the CO A-X bands, so that an operational method results to search for µ-variation. The data from both experiments were used to perform an improved analysis of the perturbations in the A¹ , v=0 and 1 levels by vibrational levels in the D¹ , I^{1 -}, e^{3 -}, d³ , and a'^{3 +} states. The object Q1237+064 will be observed in May 2013, aiming for a good signal-to-noise spectrum containing the CO A-X bands as well as the H₂ Lyman and Werner bands. This should result in an accurate and robust constraint on µ/µ.