Low temperature photoluminescence of Cs2NaY1−xErxCl6 excited by synchrotron radiation

► Synchrotron radiation as pumping source extend optical spectroscopy into VUV range. ► 10 K and RT optical spectroscopy of Cs2NaErxY1−xCl6 was investigated in detail. ► Quenching of emission from 4G11/2 at RT leads to visible emission at 10 K from 4S3/2. ► The red emission from 4F9/2 is much weaker at 10 K.