PERMLINK: www.lxcat.net/UBC

DESCRIPTION: The UBC database consists of Absolute Dipole (Optical) Oscillator Strengths as a function of Photon Energy for 65 neutral atoms and molecules for photoabsorption in the vacuum UV and soft X-ray regions of the electromagnetic spectrum. The data were obtained in both the discrete and continuum regions by fast electron scattering using electron energy loss spectroscopy (EELS) at zero degrees scattering angle. This method, known as Dipole (e,e) Spectroscopy, involves Bethe-Born conversion of the electron scattering intensities and Sum-Rule normalization to give absolute scales. The technique utilizes the virtual photon field created by a fast electron scattered in the forward direction (i.e. at negligible momentum transfer). Under these conditions the electron energy loss is equivalent to the photon energy and the method gives results entirely equivalent to those that could be obtained using continuum light sources such as monochromated synchrotron radiation. It is important to note that our data do not suffer from the linesaturation effects (linewidth-bandwidth interactions) which can cause large errors in optically determined oscillator strengths for discrete transitions with narrow natural linewidths. Our experimental methods, data processing and some corrections to earlier data are presented in the following publications: (1) W.F. Chan, G. Cooper and C.E. Brion, Absolute Oscillator Strengths for the Electronic Excitation of Atoms at High Resolution: Experimental Methods and Measurements for Helium. Phys. Rev. A 44,186-204 (1991). (2) W.F. Chan, G. Cooper, X. Guo, G.R. Burton and C.E. Brion, Absolute Oscillator Strengths for the Electronic Excitation of Atoms at High Resolution. Part III: The Photoabsorption of Argon, Krypton and Xenon. Phys. Rev. A 46, 149-171 (1992); 48, 858-860 (1993). (3) T.N. Olney, N.M. Cann, G. Cooper, and C.E. Brion. Absolute Scale Determination for Photoabsorption Spectra and the Calculation of Molecular Properties using Dipole Sum-Rules. Chem.Physics, 223, 59-98 (1997) and references therein. Both “low” ( typically 1.0 eV fwhm) and “high” ( typically 0.048 eV fwhm) resolution data are tabulated and can be plotted. These data are derived from a series of measurements made by Professor Chris Brion and his group at the University of British Columbia (UBC) between 1991 and 2002. References to their publications for specific neutral species should be included in all publications making use of these data. See the UBC database for specific references. Occasionally, the tabulated values of oscillator strength are negative below and close to threshold for inelastic scattering. This simply reflects the statistical accuracy of the data.

OSCILLATOR STRENGTHS