Retrieval of the complex-valued refractive index of germanium near the M_4,5 absorption edge

Abstract

The complex-valued index of refraction of germanium in the extreme ultraviolet (XUV) is measured by multiangle reflectance of synchrotron radiation. The resulting index of refraction is higher resolution than previously measured values. It reveals new structures attributed to transitions from the 3d-core orbitals to the Σ c 5,2 and the X c 5,2 conduction bands. Additionally, it is shown that the problem of total external reflection, which renders multi-angle reflectance measurements insensitive to the complex-valued refractive index at grazing incidence, can be overcome by employing measurements at angles of incidence away from the critical angle.

Attosecond Time-Domain Measurement of Core-Level-Exciton Decay in Magnesium Oxide

“…During the measurement, the reflectivity of MgO and a calibrated gold mirror are taken sequentially allowing signal normalization and thus obtaining the absolute reflectivity of MgO. The reflectivity is a combination of both the real and imaginary parts of the refractive index, which makes its direct interpretation difficult [16]. We therefore extract the absorption spectrum, shown in Fig.…”

Attosecond spectroscopy for the investigation of ultrafast dynamics in atomic, molecular and solid-state physics

“…This dependence further complicates the physical interpretation of an ATRS trace too. While the absorption properties of a material are related to the real part of its dielectric function solely, the reflection coefficient depends on both the imaginary and real part [329], with a sensitivity that changes with the incidence angle.…”

Extreme Ultraviolet Reflection–Absorption Spectroscopy: Probing Dynamics at Surfaces from a Molecular Perspective

“…Although this report is focused primarily on the first row transition metal oxides, the resonant attenuation length of XUV light is similarly low for many materials, 38 indicating this technique can be applied more generally to probe surface dynamics in a wide range of material systems. XUV spectroscopy in a reflection geometry can also be used measure complex dielectric functions in the XUV region 39 and is sensitive to changes in the nonresonant photoionization cross-section of materials. 40 It should be noted that line shapes differ for reflection spectra compared to absorption spectra because absorption depends only on the imaginary component of the refractive index while reflection depends on the complex refractive index.…”