Geology Reference
In-Depth Information
2.5
Energy curve for blackbody at 6000K
Solar irradiance curve outside atmosphere
Solar irradiance curve at sea level for a
zenith angle of 0
°
O
H
2
O
O
2
H
2
O
H
2
O
2.0
O
3
1.5
1.0
H
2
O
H
2
O
UV
0.5
H
2
O
H
2
O
CO
2
O
3
Visible
Infrared
0
0 200
600
1000
1600
2000
2600
3000
Wavelength (nm)
Figure 4 Solar flux outside the atmosphere and at sea level, respectively. The emission of a
blackbody at 6000 K is included for comparison. The species responsible for light
absorption in the various regions (O
2
,H
2
O, etc.) are also shown (after ref. 60)
intensity or spherical radiant flux, viz
F
l
ð
l
Þ¼
Z
L
l
ð
l
;
W
;
j
Þ
do
ð
2
:
1
Þ
where L
l
(l) (cm
2
s
1
sr
1
nm
1
) denotes the spectral photon radiance,
o is the solid angle and (W, j) are the polar and azimuthal angles of
incidence of the radiation interacting with the molecule of interest. In
essence, all angles of incident light must be considered when measuring
or calculating the actinic flux (i.e. W
¼
0-1801, o
¼
0-3601). Photolysis
rates are often expressed as a first-order loss process, e.g.
in the
photolysis of NO
2
NO
þ
O(
3
P)
NO
2
þ
hn
-
(2.2)
i.e.
d
½
NO
2
dt
¼
j
2
:
2
½
NO
2
ð
2
:
3
Þ
where the photolysis frequency, j, can be expressed as
j
¼
Z
l
max
s
ð
l
;
T
Þ
f
ð
l
;
T
Þ
F
l
ð
l
Þ
dl
ð
2
:
4
Þ
l
min
