We have developed a polarizing undulator-based optical system for natural circular dichroism (CD) measurement and succeeded in the observation of natural circular dichroism in the extreme vacuum ultraviolet (EUV) region.

CD has been utilized to analyze the structure of chiral molecules and polymers. The extension of the CD-measurable region to the EUV region has made a significant increase in the number of the CD-applicable molecules such as sugars. However, in the EUV region, no continuous transparent-type optics is currently available. Therefore, the EUV-CD measurement system without transmission-type optics has been developed at the beam line BL-5B in the storage ring TERAS at AIST in Japan, which has adopted a polarizing undulator as a circularly polarized light source. The intensity of CD is generally weak, approximately 0.1-1 % of absorption intensity. Such a weak CD signal was successfully acquired by an appreciable improvement in our undulator-based CD system and calibration method.