| Autor: |
Hughes PP; National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA., Beasten A; Nuclear Engineering Program, University of Maryland, College Park, Maryland 20742, USA., McComb JC; Nuclear Engineering Program, University of Maryland, College Park, Maryland 20742, USA., Coplan MA; Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA., Al-Sheikhly M; Nuclear Engineering Program, University of Maryland, College Park, Maryland 20742, USA., Thompson AK; National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA., Vest RE; National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA., Sprague MK; National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA., Irikura KK; National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA., Clark CW; National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA. |
| Abstrakt: |
In the course of investigations of thermal neutron detection based on mixtures of (10)BF3 with other gases, knowledge was required of the photoabsorption cross sections of (10)BF3 for wavelengths between 135 and 205 nm. Large discrepancies in the values reported in existing literature led to the absolute measurements reported in this communication. The measurements were made at the SURF III Synchrotron Ultraviolet Radiation Facility at the National Institute of Standards and Technology. The measured absorption cross sections vary from 10(-20) cm(2) at 135 nm to less than 10(-21) cm(2) in the region from 165 to 205 nm. Three previously unreported absorption features with resolvable structure were found in the regions 135-145 nm, 150-165 nm, and 190-205 nm. Quantum mechanical calculations, using the TD-B3LYP/aug-cc-pVDZ variant of time-dependent density functional theory implemented in Gaussian 09, suggest that the observed absorption features arise from symmetry-changing adiabatic transitions. |
