15min:

K. KUYANOV-PROZUMENT, A. P. COLOMBO, Y. ZHOU, G. B. PARK, V. S. PETROVIC´ AND R. W. FIELD, Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139.

Chirped Pulse millimeter-Wave (CPmmW) spectroscopy, an extension of Brooks Pate's Chirped Pulse Fourier Transform Microwave (CP-FTMW) technique, has been adapted to observe electronic transitions between Rydberg states. The feasibility of this method has been demonstrated on calcium atoms of effective principal quantum number n^* of 40 and at frequencies of 70--84 GHz. Whereas Rydberg states are generally detected by ionization, we directly observe the free induction decay that they emit after polarization by the chirped pulse. Spectra with a bandwidth of 10 GHz and resolution of 1 MHz or better may be acquired in several shots, which could enable high-resolution ``pure electronic'' spectroscopy of molecules in core-nonpenetrating Rydberg states. The available millimeter-wave power is not a limitation in this experiment because the transition dipole moments are large ( 5,000 Debye). Furthermore, the ability to quickly and arbitrarily polarize the sample opens avenues for optical plus millimeter-wave coherent experiments. Schemes to extend this technique to molecules are under development.