Abstract: Surface pressure-area isotherm(π-A) behaviour of the mixture of metal complex hexadecyl pyridinium tetrakis(α-thenoyltrifluoroacetone) europium[C₅H₅NC₁₆H₃₃Eu(TTA)₄] (Ⅰ) and stearic acid(Ⅱ) with the molar ratio 1:1,1:2,1:4,1:8 and 1:12 was investigated.The experimental zero-pressure molecular areas obtained from different molar ratio are well consistent with the calculated ones according to the equation of A_cakd= 55i/(i+j)+22j/(i+j), where i/(i+j), j/(i+j) are molar fraction of Ⅰ and Ⅱ, 55 and 22 are molecular areas of Iand Irespectively.Z-type Langmuir-Blodgett film from a mixture of Ⅰ:Ⅱ=1:4 was deposited on quartz plate at the surface pressure of 20 mN/m and studied by using UV, fluorescence spectrometry and low angle X-ray diffractometry.UVspectrum of the film peaked at 220, 232, 264 and 328 nm, which is similar to those of chloroform solution of the complex.However, the relative strength ratio of each peak changed and both peaks at 264 and 328 nm are somewhat blue shift comparing with that obtained from chloroform solution, it may be due to the order of the molecular arrangment in the film.Fluorescence spectrum of the film shows the three characteristic peaks of Eu(Ⅲ) complex, locating at 594, 613.5, and 652 nm which is corresponding to magnetic dipole transition⁵D₀→⁷F₁, induced electronic dipole transition⁵D₀ →⁷K₂ and ⁵D₀→⁷F₃ transition, while those for powder complex appear at 594, 612 and 666 nm, respectively.Low angle X-ray diffraction results in four Bragg peaks, and based on these data the film thickness per layer 4.27 nm is calculated.

Key words: Europium (Ⅱ) complex, α-thenoyltrifkioroacetone, LB film