Tunable Raman photons in singly charged p-doped quantum dots

The obtention of spontaneous Raman photons is analyzed in singly charged p-doped quantum dots in the absence of an external magnetic field. The use of a far detuned single driving laser allows to obtain a Raman photon line which exhibits subnatural linewidth, and whose center can be tuned by changing the detuning and/or the Rabi frequency of the driving field. The Raman photons are produced along the undriven transition and they arise from the weak interaction of the trion states with the nuclear spins. The operating point for the gate voltage of the heterostructure can also be used to modify the linewidth and the peak value of the fluorescent signal.

Ammonia observations of the nearby molecular cloud MBM 12

We present NH_3(1,1) and (2,2) observations of MBM 12, the closest known molecular cloud (65-pc distance), aimed at finding evidence for on-going star formation processes, No local temperature (with a T_rot upper limit of 12 K) or linewidth enhancement is found, which suggests that the area of the cloud that we have mapped (∼ 15-arcmin size) is not currently forming stars. Therefore this nearby 'starless' molecular gas region is an ideal laboratory to study the physical conditions preceding new star formation. A radio continuum source has been found in Very Large Array archive data, close to but outside the NH_3 emission. This source is likely to be a background object.