A thickness independent radiochromic film dosimetry system

A new radiochromic thin film dosimeter has been developed for use in radiation processing. The dosimeter's properties are similar to those of the commercially available FWT-60-00 Radiochromic Detectors with three key differences: 1) a lower sensitivity allows reading the optical density at the peak of the absorbtion spectrum (ca. 600 nm) for absorbed doses to over 50 kGy, 2) a radiation-insensitive dye additive allows for automatic thickness correction, and 3) another additive extends to higher doses the agreement between gamma and E-beam calibrations. The dosimeter is analyzed for its sensitivity, temperature and humidity dependencies, stability, reproducibility, and agreement of gamma and E-beam calibrations.     

Nonlinear absorption by quantum interference in cold atoms

We report an experimental observation of third-order nonlinear absorption by quantum interference in (87)Rb atoms cooled and confined in a magneto-optic trap. A coupling laser creates electromagnetically induced transparency (EIT) in a multilevel Rb system in which the third-order nonlinear absorption is enhanced by constructive quantum interference while the linear absorption is inhibited by destructive interference. Our experiment demonstrates the EIT system proposed by Harris and Yamamoto [Phys. Rev. Lett. 81, 3611 (1998)], which absorbs two photons but not one photon in the dressed-state picture.     

Tricarbonylchromium complexes of some substituted 9,10-dihydro-9,10-o-benzenoanthracenes

Tricarbonylchromium complexes of 9,10-dihydro-l,4-dimethoxy-9,10-o-benzenoanthracene and 9,10-dihydro-l,4-dimethyl-9,10-o-benzenoanthracene have been prepared and characterized. Under the given experimental conditions, the dimethoxy ligand forms two isomeric complexes. These have been separated by both analytical and preparative scale liquid chromatography. Structures have been tentatively assigned on the basis of experiments with the NMR shift reagent EuFod₃. The methyl substituted ligand forms three isomeric complexes.     

Characterization of [Re2Cl3(μ-dppm)2(NCCH3)2][Cl] and [Re2Cl3(μ-dppm)2(NCC6H5)2][Cl]·2CH2Cl2 by X-ray Crystallographic and Two-Dimensional NMR Spectroscopic Techniques

The complex Re₂Cl₆(P-n-Bu₃)₂ prepared in situ reacts with CH₃CN to form a blue-green solution. Addition of the chelating phosphine bis(diphenylphosphino)methane (dppm) results in the formation of the complex [Re₂Cl₃(-dppm)₂(NCCH₃)₂][Cl] (1) upon heating. The two acetonitrile molecules adopt a trans geometry on the rhenium center with the axially coordinated chlorine. The analogous trans benzonitrile species [Re₂Cl₃(-dppm)₂(NCC₆H₅)₂][Cl]·2CH₂Cl₂ (2) is synthesized under the same reaction conditions. The coupling constants of the AABB ³¹P{¹H} NMR spectra of the compounds were elucidated from ³¹P–³¹P homonuclear J-resolved NMR experiments. Additional characterization methods include ³¹P{¹H} NMR spectroscopy, UV-vis spectroscopy, and X-ray crystallography.     

Opti-Chromic dosimeters for low-dose applications (0.1 Gy to 10 kGy)

Opti-chromic dosimeters have been developed which measure absorbed doses to as low as 0.1 Gy. These detectors consists of a radiation sensitive solution contained in fluorinated ethylene-propylene (FEP) tubing by borosilicate beads. Three formulations are presented, covering a range of absorbed doses from 0.1 to 3000 Gy.