Narrow 87Rb and 133Cs hyperfine transitions in evacuated wall-coated cells

An extension of work on wall-coated cells was made to include observation by a triple resonance technique of the 0-0 hyperfine transitions in 87Rb and 133Cs. Conventional RF excited lamps were used. Interest in such cells is for possible application in atomic clocks. The Rb cell would appear to remain especially promising in this respect

Children's suggestibility in relation to their understanding about sources of knowledge

In the experiments reported here, children chose either to maintain their initial belief about an object's identity or to accept the experimenter's contradicting suggestion. Both 3– to 4–year–olds and 4– to 5–year–olds were good at accepting the suggestion only when the experimenter was better informed than they were (implicit source monitoring). They were less accurate at recalling both their own and the experimenter's information access (explicit recall of experience), though they performed well above chance. Children were least accurate at reporting whether their final belief was based on what they were told or on what they experienced directly (explicit source monitoring). Contrasting results emerged when children decided between contradictory suggestions from two differentially informed adults: Three– to 4–year–olds were more accurate at reporting the knowledge source of the adult they believed than at deciding which suggestion was reliable. Decision making in this observation task may require reflective understanding akin to that required for explicit source judgments when the child participates in the task

Diode laser 87Rb optical pumping in an evacuated wall-coated cell

The evacuated wall coated sealed cell coupled with diode laser optical pumping offers a number of attractive potential advantages for use in Rb or Cs atomic frequency standards. An investigation of systematic effects is required to explore possible limitations of the technique. The use of diode laser optical pumping of 87 Rb in an evacuated wall coated sealed cell is presented. Experimental results/discussion to be presented include the signal strength and line broadening of the 0 - 0 hyperfine resonance as a function of light intensity for the D1 optical transitions (F - F prime) - (2 1 prime) and (2 - 2 prime), shift of the 0 - 0 hyperfine frequency as a function of laser intensity and de-tuning from optical resonance, and diode laser frequency stabilization techniques

A Spectropolarimetric Atlas of Seyfert 1 Galaxies

We present optical spectropolarimetry of the nuclei of 36 Seyfert 1 galaxies, obtained with the William Herschel and the Anglo-Australian Telescopes from 1996 to 1999. In 20 of these, the optical emission from the active nucleus is intrinsically polarized. We have measured a significant level of polarization in a further 7 objects but these may be heavily contaminated by Galactic interstellar polarization. The intrinsically polarized Seyfert 1s exhibit a variety of characteristics, with the average polarization ranging from < 0.5 to 5 per cent and many showing variations in both the degree and position angle of polarization across the broad H alpha emission line. We identify a small group of Seyfert 1s that exhibit polarization properties similar to those of Seyfert 2 galaxies in which polarized broad-lines have been discovered. These objects represent direct observational evidence that a Seyfert 2-like far-field polar scattering region is also present in Seyfert 1s. Several other objects have features that can be explained in terms of equatorial scattering of line emission from a rotating disk. We propose that much of the diversity in the polarization properties of Seyfert galaxies can be understood in terms of a model involving both equatorial and polar scattering, the relative importance of the two geometries as sources of polarized light being determined principally by the inclination of the system axis to the line-of-sight.Comment: Accepted for publication in MNRAS (28 pages, 25 figures

Is J 133658.3-295105 a Radio Source at z >= 1.0 or at the Distance of M 83?

We present Gemini optical imaging and spectroscopy of the radio source J 133658.3-295105. This source has been suggested to be the core of an FR II radio source with two detected lobes. J 133658.3-295105 and its lobes are aligned with the optical nucleus of M 83 and with three other radio sources at the M 83 bulge outer region. These radio sources are neither supernova remnants nor H II regions. This curious configuration prompted us to try to determine the distance to J 133658.3-295105. We detected H_alpha emission redshifted by ~ 130 km s^-1 with respect to an M 83 H II region 2.5" east-southeast of the radio source. We do not detect other redshifted emission lines of an optical counterpart down to m_i = 22.2 +/- 0.8. Two different scenarios are proposed: the radio source is at z >= 2.5, a much larger distance than the previously proposed lower limit z >= 1.0, or the object was ejected by a gravitational recoil event from the M 83 nucleus. This nucleus is undergoing a strong dynamical evolution, judging from previous three-dimensional spectroscopy.Comment: 6 pages, 4 figure

Effects of T=0 two body matrix elements on M1 and Gamow-Teller transitions: isospin decomposition

We perform calculations for M1 transitions and allowed Gamow Teller (GT) transitions in the even-even Titanium isotopes - $^{44}$Ti, $^{46}$Ti, and $^{48}$Ti. We first do calculations with the FPD6 interaction. Then to study the effect of T=0 matrix elements on the M1 and GT rates we introduce a second interaction in which all the T=0 matrix elements are set equal to zero and a third in which all the T=0 matrix elements are set to a constant. For the latter two interactions the T=1 matrix elements are the same as for FPD6. We are thus able to study the effects of the fluctuating T=0 matrix elements on M1 and GT rates

Thermal Emission from HII Galaxies: Discovering the Youngest Systems

We studied the radio properties of very young massive regions of star formation in HII galaxies, with the aim of detecting episodes of recent star formation in an early phase of evolution where the first supernovae start to appear. Our sample consists of 31 HII galaxies, characterized by strong Hydrogen emission lines, for which low resolution VLA 3.5cm and 6cm observations were obtained. The radio spectral energy distribution has a range of behaviours; 1) there are galaxies where the SED is characterized by a synchrotron-type slope, 2) galaxies with a thermal slope, and, 3) galaxies with possible free-free absorption at long wavelengths. The latter SEDs were found in a few galaxies and represent a signature of heavily embedded massive star clusters closely related to the early stages of massive star formation. Based on the comparison of the star formation rates determined from the recombination lines and those determined from the radio emission we find that SFR(Ha) is on average five times higher than SFR(1.4GHz). We confirm this tendency by comparing the ratio between the observed flux at 20 cm and the expected one, calculated based on the Ha star formation rates, both for the galaxies in our sample and for normal ones. This analysis shows that this ratio is a factor of 2 smaller in our galaxies than in normal ones, indicating that they fall below the FIR/radio correlation. These results suggest that the emission of these galaxies is dominated by a recent and massive star formation event in which the first supernovae (SN) just started to explode. We conclude that the systematic lack of synchrotron emission in those systems with the largest equivalent width of Hb can only be explained if those are young starbursts of less than 3.5Myr of age.Comment: Accepted for publication in Ap