α\alpha-particle condensate states in 16^{16}O

The existence of a rotational band with the $\alpha$+$^{12}$C($0_2^+$) cluster structure, in which three $\alpha$ particles in $^{12}$C($0_2^+$) are locally condensed, is demonstrated near the four-$\alpha$ threshold of $^{16}$O in agreement with experiment. This is achieved by studying structure and scattering for the $\alpha$+$^{12}$C($0_2^+$) system in a unified way. A drastic reduction (quenching) of the moment of the inertia of the $0^+$ state at 15.1 MeV just above the four-$\alpha$ threshold in $^{16}$O suggests that it could be a candidate for the superfluid state in $\alpha$-particle condensation.Comment: 5 pages, 3 figure

DIRECT OBSERVATION OF RYDBERG{--}RYDBERG TRANSITIONS IN CALCIUM ATOMS

Author Institution: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139Chirped 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 ($\sim$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