Optogalvanic Signals From Argon Metastables In A Rf Glow-Discharge

Laser optogalvanic (LOG) signals at 667.7, 751.5, and 696.5 nm from the 3 P 1 and 3 P 2 levels of Ar were studied at a pressure of 250 mTorr in a rf glow discharge. Signals with unexpected signs and time dependences were found. The results are interpreted as being due to radiative trapping effects and collisional mixing between resonance and metastable levels. An average electron energy of 2.1 eV is derived from modeling the data

HYPERFINE MAGNETIC FIELDS ON DILUTE ACTINIDES IN IRON

Nous avons mesuré le champ magnétique hyperfin créé par le thorium et l'uranium dilué dans le fer. Les mesures ont eu lieu à l'aide de la technique des perturbations de corrélation angulaire après une implantation ionique. Pour le thorium dans le fer à la température ambiante, le champ est de — 230 ± 80 kOe, et pour l'uranium dans le fer de — 580 ± 150 kOe. Le signe et l'ordre de grandeur des valeurs mesurées suggèrent que la contribution de la couche 5 f au champ total, est petite dans le cas de l'uranium, et donc différente de la contribution de la couche 4 f dans le cas des terres rares. Des résultats récents pour Np dans le nickel (Heff = + 170 kOe) et pour Pu dans le fer (Heff = + 620 kOe) montrent que, pour les actinides, les champs ne suivent pas la tendance qui apparaît pour la série des terres rares.We have measured the hyperfine magnetic field on dilute thorium and uranium in iron metal using the ion implantation perturbed angular correlation technique. The field on thorium in iron at room temperature is — 230 ± 80 kOe and on uranium in iron — 580 ± 150 kOe. The sign and magnitude of the values suggests that the 5 f contribution to the field for uranium is small, unlike the 4 f contribution for the rare earths. Recent results for Np in nickel (Heff= + 170 kOe) and for Pu in iron (Heff = + 620 kOe) indicate that fields on actinides do not follow the trend apparent for the rare earth series

Field Isotope Shifts In The 3p⁵4p-3p⁵5d 604.3 Nm Transition In Argon I

The authors have measured the isotope shifts between ³⁶,³⁸,⁴⁹Ar I using Doppler-free intermodulated optogalvanic spectroscopy on the 4p-5d transition at 604.3 nm. A field shift which is 60% greater than that of a 4s-4p transition previously measured was observed. The large relative field shift in the case of an atom of such low Z is surprising and not yet explained by any calculation

Influence of humidity on photochemical ozone generation with 172 nm xenon excimer lamps

The reaction kinetics of photochemical ozone (O3) generation in humid air and oxygen (O2) using efficient, narrow band vacuum ultra violet (VUV) 172 nm xenon excimer lamps is discussed. Trace amounts of water (H2O) vapor in the process gas leads to hydroxyl (OH) and hydroperoxy (HO2) radical formation. These radicals drive a catalytic O3 destruction cycle limiting O3 saturation concentration. This catalytic O3 destruction cycle was included into a quantitative kinetic model describing photochemical O3 production. Experimental O3 saturation concentrations obtained with coaxial VUV driven photochemical O3 generators compare satisfactorily with the models predictions

Placental Pathology and Neuroimaging Correlates in Neonates with Congenital Heart Disease.

Abstract Congenital heart disease (CHD) is an independent risk factor for brain injury, including stroke, and poor neurodevelopmental outcomes, and placental abnormalities may represent an additional risk factor for brain injury in neonates. The incidence and scope of placental pathology and relationship to fetal brain abnormalities in pregnancies complicated by fetal CHD has not been explored to our knowledge. In order to determine the prevalence of placental pathology findings and whether placental findings are associated with postnatal brain injury in pregnancies complicated by fetal CHD, we reviewed placental pathology reports for 51 pregnancies complicated by CHD and scored available postnatal, pre-operative brain MRI for brain pathology. Overall, 57% of CHD infants had abnormal placental pathology. Pregnancies complicated by CHD with aortic obstruction (AO) were significantly more likely than those with no obstruction to have abnormal placental pathology (79% vs. 44%). There was a trend toward more severe brain lesions amongst patients with brain lesions and placental abnormality (55% moderate/severe) compared to those without placental abnormality (11% moderate/severe). These data suggest that placental abnormalities are common in CHD and may have a compounding effect on brain lesions in this high-risk population