In ). In contrast, the 808 nm laser light irradiation at 10 K on metastable HS Fe(II) for 90 min lowered the T value from 2.36 cm 3 mol -1 K to 0.69 cm 3 mol -1 K, which indicated that the metastable HS Fe(II) state might be reversibly transformed back into the LS state when 808 nm light was used on sample -confirming the reverse LIESST effect (Fig. ). 220 K. Upon further increase in temperature, the intensity decreased further (Fig. ).