A series of Rare Earth (R.E.) trifluoroacetate crystals [Re(CF

3

COO)

3

· 3H

2

O]

2

(Re = Eu

Gd

Tb

Dy) and [Tb

x

Y

1-x

(CF

3

COO

3

3H

2

O]

2

were prepared with hydrosolution method in room temperature; The crystal structure of this type of compounds has been determined with Nicolet R

3M/E

type Four Circle Diffractometer

which is monoclinic. The space group is P

21/c

. The R.E. trifluoroacelates have a dimeric structure [Re(CF

3

COO)

3

·3H

2

O]

2

viz. Z = 2. The characteristic spectral properties of stoichiometry compounds CRe(CF

3

COO)

3

·3H

2

O]

2

(Re= Eu

Gd

Tb

Dy) are discussed in detail. In the emission spectra

the Eu

3+

shows 1

3

5 lines corresponding to

5

D

0

-

7

F

2

1

2 transition respectivly

where the

5

D

0

-

7

F

2

transition shows stronger emission at 612nm. The number and intensities of the lines are in agreement with C

2

orCsUnder ultraviolet excitation

the red emission (612nm) of the Eu

3+

the green emission (544nm) of the Tb

3+

the blue (480-488nm) and yellow(572-577nm) of Dy

3+

and ultraviolet emission (312nm) of Gd

3+

are observed in this type of crystal.The spectral intensities of [Tb

x

Y

1-x

(CF

3

COO)

3

·3H

2

O]

2

(x=0.05

0.10

0.15

0.20

0.25mol depend on the concentration of Tb

3+

. No fluorescence quenching occurs.