The paper reports determinations of rate constants for the physical deactivation of O
2
(
1
Δ
g
) by gases present in the atmosphere. A modified discharge-flow technique was employed, and relative concentrations of O
2
(
1
Δ
g
) were measured by a photoionization method. The rate constants for the process O
2
(
1
Δ
g
) ) + M → O
2
+ M (1) were ≤1.1 x 10
-19
, ≤ 2.1 x 10
-19
, ~2.4 x 10
-18
, ~3.9 x 10
-18
, ~ 1.5 x 10
-17
(cm
3
molecule
-1
s
-1
) for M = N
2
, Ar, O
2
, CO
2
, H
2
O respectively. The rate constant for quenching by dry air was measured directly to be 4.3 ± 0.7 x 10
-19
cm
3
molecule
-1
s
-1
; this value is consistent with the most recent estimate based on [O
2
(
1
Δ
g
)] in the upper atmosphere (3.5 ±1.0 x 10
-19
cm
3
molecule
-1
s
-1
; W. F. J. Evans, private communication). Wall deactivation efficiencies varied from 1.2 x 10
-5
to 2.3 x 10
-5
.
