Laser spectroscopy of molecules

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We have recently achieved reliable production of molecules with translational temperatures at the millikelvin level. One of the most promising applications for such ultracold molecules is high-resolution laser spectroscopy. In this project we will perform what will be, to our knowledge, the first experiment of this type. In particular, we will demonstrate laser spectroscopy of vibrational transitions in the HD+ molecule, concentrating on an overtone transition at a wavelength of 1.4(m . The HD+ molecule is of fundamental importance because it is one of the simplest molecules, containing just a single electron. Precise measurement of vibrational transition frequencies will ultimately allow (i) to test theoretical methods of precision calculation of molecular levels; (ii) to demonstrate the existence of QED effects in molecules; (iii) to determine the ratio of electron-to-proton mass in a novel way and with potentially higher precision than with alternative methods; (iv) to measure nuclear properties such as quadrupole moments, (v) to test the time-independence of nuclear mass ratios. The two-year goal consists in achieving a spectral resolution at a level of 10-8 such that the gross features of the hyperfine structure can be resolved, and in obtaining an absolute measurement of a few rotational-vibrational transition frequencies with a similar precision. This will be performed by means of a femtosecond frequency comb. An investigation of systematic effects will be performed in order to establish the accuracy. The methods developed in our project will also be applicable to a large variety of other molecular ions.