The photoacoustic spectral study of energy transfer between two rare earth ions in phosphor are first reported. Combined with photoluminescent spectra (PLS) and photoacoustic spectra (PAS)

the mechanism of sensitization of Ce

3+

to Tb

3+

and quenching of Tm

3+

to Er

3+

in LaOBr are discussed. In phosphor LaOBr:Tb

Ce

under 365nm excitation

the emissions of Tb

3+

are enhanced obviously by Ce

3+

and the photoacoustic peak of Ce

3+

increases. It suggests that the sensitization of Ce

3+

to Tb

3+

is phonon assisted energy transfer. In LaOBr:Er

Tm system

the visible emission (green:

4

S

3/2

-

4

I

15/2

red:

4

F

9/2

-

4

I

15/2

) of Er

3+

are quenched by co-doped Tm

3+

. Among four main photoacoustic peaks of Er

3+

the intensities of PA peaks at 527nm and 646nm which correspond to the absorption of energy levels

2

H

11/2

and

4

F

9/2

of Er

3+

respectively increase obviously with Tm

3+

while other two (372nm and 486nm )keep constant. Our results not only confirm that the cross relaxation of Er

3+

:

4

S

3/2

-

4

F

9/2

11/2

and Tm

3+

:

3

H

6

-

3

H

4

5

causes the quenching of visible emissions of Er

3+

but also suggest that there exists another cross relaxation of Er

3+

:

4

F

9/2

-

4

I

13/2

and Tm

3+

:

3

H

6

-

3

H

5

which raises the quenching of red emission of Er

3+

.