Dielectric Properties of KCl, KBr, and KI Single Crystals in the Extreme Ultraviolet up to 35 eV

Abstract

The reflectance of freshly cleaved single crystals of KCI, KBr, and K I has been measured for 15" angle of incidence a t room temperature for photon energies between 5 and 35 eV, using the continuous spectrum of synchrotron radiation. For photon energies from 12 t o 30eV the optical constants, the dielectric constant, and the energy loss function were determined by reflectance measurements with parallel polarized light a t several angles of incidence between 15' and 75". A prominent doublet near 20 eV is found for all potassium halides. It is assigned to excitonic transitions from the K+3p core level to the conduction band a t r a n d X . Energy differences between some critical points a t T and X are estimated

Dielectric Properties of the Rubidium Halide Crystals in the Extreme Ultraviolet up to 30 eV

“…Because of errors in the absolute reflectivity and the extrapolation the computed absolute values for el and E, are not expected to be as accurate as values obtained by the multi-angle reflection method, which, in the case of alkali halides, has only been used for the potassium halides in the same energy range . [23]. An inaccurate normalization of the reflectivity by the same factor over the whole energy range does not affect the computed phase but changes the absolute values for and E, when equation (3) is used.…”

Fine structure of the extreme ultraviolet spectra of the potassium halide crystals at 10 °K

“…The spin-orbit splitting of the 3p level of the free K + ion is of the same magnitude (0.26 eV) [14]. The splitting was already indicated a t room temperature in the case of K I as a shoulder in t,he reflection spectrum [8] and a weak double maximum in the photo-yield [lo]. A corresponding splitting has been observed in electron energy loss spectra of KBr a t low temperature [15].…”

Potassium Iodide (KI)

“…Additional measurements of the Urbach edge coveting the temperature range from 300 to 900 K are reported by Matienssen [4]. (1) and (2). 1 for this spectral region are generated using Eqs.…”

“…1 for this spectral region are generated using Eqs. A Sellmeier model of the form /~2AEi(T) nz(A,T)-1 + ~ A2 -A2i(T) 1 (3) is used to represent the data accurately. The room-temperature (20 ~ C) index of refraction from the ultraviolet to the far infrared (0.25 to 50/,m) has been determined by Li [5] using data from a variety of different sources.…”