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We theoretically study the ionization enhancement of the diatomic molecular ion H2+ at two critical internuclear distances R, using orthogonal two-color laser fields. The polarization of the fundamental infrared laser field and a weak second-harmonic field is parallel and perpendicular to the molecular axis, respectively. It is observed that adding the second-harmonic field raises slightly the first ionization peak at the smaller critical R, whereas it enhances the second one at the larger critical R significantly. We further analyze the observable evidence which distinguishes two underlying mechanisms responsible for the enhanced ionization of H2+: (i) the resonant excitation along with the coherent interference of the ionizing wave packets from the 1sσg and 2pσu states and (ii) the easier ionization from the up-field site of the molecule.

Francia, Bd. 34, Nr. 3 (2007)

We theoretically investigate the deformation of atomic p± orbitals driven by strong elliptically polarized (EP) laser fields and the role it plays in tunnel ionization. Our study reveals that different Stark effects induced by orthogonal components of the EP field give rise to subcycle rearrangement of the bound electron density, rendering the initial p+ and p− orbitals deformed and polarized along distinctively tilted angles with respect to the polarization ellipse of the EP field. As a consequence, the instantaneous tunneling rates change such that for few-cycle EP laser pulses the bound electron initially counterrotating (corotating) with the electric field is most likely released before (after) the peak of the electric field. We demonstrate that with a sequential-pulse setup one can exploit this effect to spatially separate the photoelectrons detached from p+ and p− orbitals, paving the way towards robust control of spin-resolved photoemission in laser-matter interactions.

A gross morphological study of the brain of the African giant pouched rat (Cricetomys gambianus Waterhouse, 1840) was undertaken in order to document its normal features and assess the structure-function paradigm. The study was conducted by direct observation of 29 adult African giant pouched rats' brains. In the telencephalon, the cerebral cortex was devoid of prominent gyri and sulci, but the large olfactory bulb and tract relaying impulses to the olfactory cortex were very prominent. The large size of the olfactory bulb correlated with the established sharp olfactory acuity of the rodent. In the mesencephalic tectum, the caudal colliculi were bigger than the rostral colliculi, indicating a more acute sense of hearing than sight. In the metencephalon, the cerebellar vermis, the flocculus and the paraflocculus were highly coiled and, thus, well developed. The myelencephalon revealed a better organised ventral surface than dorsal surface; the cuneate fascicle, the intermediate sulcus and the lateral sulcus were not evident on the dorsal surface, but there were clearly visible pyramids and olivary prominence on the ventral surface. In conclusion, the highly coiled cerebellar vermis, flocculus and paraflocculus, as well as the conspicuous pyramids and olivary prominence are indicative of a good motor coordination and balance in the African giant pouched rat.

Coordination d'ouvrage

AIM of this study was the assessment of the radiation exposure from preparation and application of (90)Y-Zevalin, the measurement of the dose rate at the patient, the exposure of family members as well as the determination of the activity concentration in urine of patients.Overall data from 31 therapeutic administrations carried out in four institutions were evaluated. During preparation and application of (90)Y-Zevalin the finger exposures of radiochemists, technicians, and physicians were measured. The dose rate of the patient was measured immediately after radioimmunotherapy. In patients treated in a nuclear medicine therapy unit, urine was collected over a two day period and the corresponding activity was determined. Family members of outpatients were asked to wear a dosimeter over a seven day period.During the preparation we found a maximum skin dose of 6 mSv at the average, and during application of 3 mSv, respectively. After administration of (90)Y the dose rate was 0.4 +/- 0.1 microSv/h at 2 m distance. Urine measurements yielded a cumulated 24 h excretion of 3.9 +/- 1.4% and 4.4 +/- 1.4% within 48 h, respectively, that is equivalent to 43 +/- 18 and 50 +/- 20 MBq of (90)Y, respectively. Family members received a radiation exposure of 40 +/- 14 microSv over seven days.During preparation and application of (90)Y-Zevalin appropriate radiation shielding is necessary. For family members as well as nursing staff no additional special radiation protection measures beyond those being common for other nuclear medicine procedures are necessary.