Soft X-ray absorption spectroscopy in the low-energy region explored using an argon gas window

Abstract

<jats:p>The soft X-ray region below 200 eV is important for investigating chemical and biological phenomena since it covers <jats:italic>K</jats:italic>-edges of Li and B and <jats:italic>L</jats:italic>-edges of Si, P, S and Cl. Helium gas is generally used as the soft X-ray transmission window for soft X-ray absorption spectroscopy (XAS) under atmospheric conditions. However, the helium gas window cannot be applied to XAS in the low-energy region since transmitted soft X-rays mostly consist of high-order X-rays due to the low transmission of first-order X-rays. In this study, the argon gas window is proposed as a new soft X-ray transmission window in the low-energy region. High-order X-rays are removed by the absorption of the Ar <jats:italic>L</jats:italic>-edge (240 eV), and first-order X-rays become the major contribution of transmitted soft X-rays in the low-energy region. Under atmospheric argon conditions, the double-excitation Rydberg series of helium gas (60 eV), Si <jats:italic>L</jats:italic>-edge XAS of an Si<jats:sub>3</jats:sub>N<jats:sub>4</jats:sub> membrane (100 eV) and S <jats:italic>L</jats:italic>-edge XAS of dimethyl sulfoxide gas (170 eV) are successfully measured, indicating that the argon gas window is effective for soft X-ray transmission in the low-energy region from 60 eV to 240 eV.</jats:p>