We have measured the integrated intensities of main emission lines for Tb

3+

Er

3+

Ho

3+

ions in ZnS. TbF

3

ErF

3

and ZnS:TbF

3

HoF

3

ACEL thin films (TF) at low concentration

furthermore

compared them with their transition probabilities and their ACEL characteristics at high concentration.It is found that when the concentration is low(-10-4mol)

the concentration quenching process could be neglected and transition probabilities of the main emission energy levels

5

D

4

2

H

11/2

+

4

S

3/2

5

S

2

(

6

F

4

)for Tb

3+

Er

3+

Ho

3+

ions can be determined by decay time. The transition probabilities of

5

D

4

-

7

F

5

2

H

11

/2+

4

S

3

/2-

4

I

15

/2 and

5

S

2

(

5

F

4

)-

5

I

8

are about 5300s

-1

13000s

-1

and 7700s

-1

respectively. In this case

the integrated intensities of main emission lines for Tb

3+

Er

3+

and Ho

3+

in ZnS ACELTF are approximately proportional to the transition probabilities. But the maximum brightness of ACEL in ZnS:Tb

3+

ZnS:Er

3+

and ZnS:Ho

3+

thin films is about 2300cd/m

2

1100cd/m

2

and 500cd/m

2

respectively. Therefore

the maximum brightness of ACEL in ZnS thin films doped with rare earth fluorides is not determined completely by the transition probability of rare earth ions themselves

but mainly depends on the concentration quenching process dominated by the cross-relaxation process of main emission energy level of rare earth ions.In the present paper

the intensity parameters for Tb

3+

in ZnS thin film have been obtained for the first time. They are Ω

2

=3.2×10

-19

cm

2

Ω

4

=1.6×10

19

cm

2

. Ω

6

=2.6×10

19

cm

2

. They have been used to estimate the cross-relaxation probability between Tb

3+

ions. The calculated result is in agreement with the experimental observation.