The chemicd and kinetic properties of singlet molecular oxygen in liquid phase have attracted much attention of chemists and biochemists owing to its involvement in many chemical and biological processes. This transient entity

however

had evaded direct observation until a decade ago when the 1270nm luminescence from the forbidden tiansition

1

△

g

O

2

(v=O)→

3

∑

g

-

O

2

(v=O) was detected via photosensitization in solution. The success of this measurement was achieved by using germanium photodiode (with much highei sensitivity in the infrared legion than in the visible region in contrast to photomultipliei tubes) coupled to fast

high-gain amplifiers. However

Ge photodiodes satisfying the measurement of ultra-weak 1270 nm band of O

2

(

1

△

g

) are not yet available in our country. Based on the results of Krasnovsky in direct observation of singlet oxygen emission at 1270 nm with red-sensitive PMT

it is of interest to see the feasibility to detect the (1

0) transition emission of O

2

(

1

△

g

) at 1070 nm by using PMT of S-1 photocathode with a spectral response ranging from 300 to 1150 nm

and a successful demonstration of this proposed approach is described in this paper.