New double beam spectrophotometer for microsamples. Application to hydrostatic pressure experiments

This article describes a new double beam spectrophotometer specially conceived for optical absorption measurements on low-absorbing microsamples. The available long-working distance makes this apparatus attractive for use on samples placed in special environments such as heating stages, biological cells, and particularly hydrostatic pressure cells. Its performance has been tested in optical absorption measurements for different Mn2+ and Cu2+ complexes. We applied the instrument for investigating the electronic spectrum of Cu2+ doped (CH3CH2NH3)2CdCl4 crystals under hydrostatic pressure using a Sapphire anvil cell. A salient feature of this work is the enormous redshift (1400 cm−1) experienced by the first Cl−→Cu2+ charge transfer band at 26 kbar. We briefly comment on the origin of this shift.