Optical properties of electron center in layered ionic crystals (CnH2n+1NH3)2MnCl4: n=1,2,3 irradiated with X-rays at 15 K

A new optical absorption band was found at the peak energy of 17 kcm-1 (590 nm) besides the Cl2- band (22.5 kcm-1 = 445 nm) in (CnH2n+1 NH3)2MnCl4 (n=1,2,3) irradiated with X-rays at 15 K. The absorption intensity of the new band increases with the X-ray dosage in proportion to that of the Cl2- band. The intensity thermally decreases in two steps at temperatures around 50 K and 80 K accompanying the decrease of Cl2- band. The absorption band can not be bleached by the 590 nm light (17 kcm-1) at 15 K. The band is assigned to an electron center where an electron is trapped at the ammonium head in the neighborhood of a Cl- vacancy. (author)