A quantum gas of ultracold polar molecules, with long-range and anisotropic interactions, would not only enable explorations of a large class of many-body physics phenomena, but could also be used for quantum information processing. We report on the creation of an ultracold dense gas of 40 K 87 Rb polar molecules. Using a single step of STIRAP (STImulated Raman Adiabatic Passage) via two-frequency laser irradiation, we coherently transfer extremely weakly bound KRb molecules to the rovibrational ground state of either the triplet or the singlet electronic ground molecular potential. The polar molecular gas has a peak density of 10 12 cm −3 , and an expansion-determined translational temperature of 350 nK. The polar molecules have a permanent electric 1 arXiv:0808.2963v2 [quant-ph]

The Fermi Gamma-ray Space Telescope observed the bright and long GRB090902B, lying at a redshift of z = 1.822. Together the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM) cover the spectral range from 8 keV to >300 GeV. Here we show that the prompt burst spectrum is consistent with emission from the jet photosphere combined with nonthermal emission described by a single powerlaw with photon index -1.9. The photosphere gives rise to a strong quasi-blackbody spectrum which is somewhat broader than a single Planck function and has a characteristic temperature of ∼ 290 keV. We model the photospheric emission with a multicolor blackbody and its shape indicates that the photospheric radius increases at higher latitudes. We derive the averaged photospheric radius R ph = (1.1 ± 0.3) × 10 12 Y 1/4 cm and the bulk Lorentz factor of the flow, which is found to vary by a factor of two and has a maximal value of Γ = 750 Y 1/4 . Here Y is the ratio between the total fireball energy and the energy emitted in the gamma-rays. We find that during the first quarter of the prompt phase the photospheric emission dominates, which explains the delayed onset of the observed flux in the LAT compared to the GBM. We interpret the broad band emission as synchrotron emission at R ∼ 4 × 10 15 cm. Our analysis emphasize the importance of having high temporal resolution when performing spectral analysis on GRBs, since there is strong spectral evolution.