UV, VUV and soft X-ray photoabsorption of dimethyl ether by dipole (e,e) spectroscopies

Absolute UV and VUV photoabsorption oscillator strengths (cross-sections) f or the valence shell discrete and continuum regions of dimethyl ether (CH3O CH3, DME) have been measured from 5 to 32 eV using high resolution (HR) (si milar to 0.05 eV f.w.h.m.) dipole (e,e) spectroscopy. A wide-range spectrum , spanning the UV, VUV and soft X-ray regions, from 5 to 200 eV has also be en obtained at low resolution (LR) (similar to 1 eV f.w.h.m.), and this has been used to determine the absolute oscillator strength scale by employing valence shell Thomas-Reiche-Kuhn (i.e., S(0)) sum-rule normalization. The presently reported HR and LR absolute photoabsorption oscillator strengths are compared with previously published data from direct photoabsorption mea surements in those limited energy regions where such data are available. Ev aluation of the S(-2) sum using the presently reported absolute differentia l photoabsorption oscillator strength data gives a static dipole polarizabi lity for dimethyl ether in excellent agreement (within 0.5%) with previousl y reported polarizability values. Other dipole sums S(u), (u = -1, -3, -4, -5, -6, -8, -10), and logarithmic dipole sums L,(u), (u = -1 to -6), are al so determined from the presently reported absolute differential photoabsorp tion oscillator strength data using dipole sum rules. (C) 2000 Elsevier Sci ence B.V. All rights reserved.