In this paper

we discussed the ultraviolet region of absorption spectrum of Alexandrite (BeAl

2

O

4

:Cr

3+

).The sample we used is grown by the Czochralski method

and its concentration is 0.03wt% Cr

2

O

3

.In the absorption spectrum

there are

as we know

two broad bands and a sharp line in visible region

which are the absorptions from ground state

4

A

2

to

5

T

1

4

T

2

and

2

E respectively. In ultraviolet region there are one small peak and two broad bands added to a strong background absorption. We also measured the excitation spectrum in region of 200-700nm at room temperature and confirmed the results of absorption spectrum. The positions of the small peak and two broad bands are about 365

263 and 213nm respectively.In order to fitting all energy levels

we measured absorption spectrum at low temperature (10.5K)

and obtained accurately the energies of

2

E

2

T

1

4

T

2

and

2

T

2

to ground state

4

A

2

.In the compute of crystal theory

we approximated its symmetry to octahedral symmetry. Using the strong field theory and considered configuration mixing

we fitted the parameters

B

C

D

q

to four energy levels

2

E

2

T

1

4

T

2

and

2

T

2

. The results are

B

=778cm

-1

C

=2967cm

-1

D

e

=1568cm

-1

and mean square deviation is 168cm

-1

. Then we computed all energy levels. We distinguished the energy levels with same term by Roman numerals.We can get following two conclusions: First

we can consider that the small peak at 365nm is because of the absorption from ground statr

4

A

2

to excited state

2

A

1

while the theoret'cal calculation result is at the similar position of 27695cm

-1

=361nm. Second

the broad band of absorption at 263nm comes mainly from the transition from ground state

4

A

2

to high

4

T

1

state [

4

T

1

(Ⅱ)]

and the transition from

4

A

2

to

2

T

1

(Ⅲ)also fall in this band.