4. The absolute quantum yield of photoluminescence of the AB or AB photodecay
products, B
Ã
k , is the ratio of the number of photons emitted from a volume unit
per unit time:
n
lum
hm ¼
Z k 2
k 1
n
lum
hm ðkÞdk; photon=cm
3 s
ð4:1:23Þ
or per photon pulse:
N
lum
hm ¼
Z k 2
k 1
n
lum
hm ðkÞdk; photon=cm
3 pulse;
ð4:1:24Þ
to the density of absorbed radiation calculated to be in the following forms:
U lum ðkÞ ¼ n
lum
hm ðkÞ=n hm ðkÞ
ð 4:1:25Þ
and
U lum ðkÞ ¼ N
lum
hm ðkÞ=N hm ðkÞ;
ð4:1:26Þ
respectively, where n
lum
hm ðkÞ and N
lum
hm ðkÞ is the luminescence spectrum in the k 1 -
k 2 spectral range expressed in photon/cm
3
Á s Á nm and photon/cm
3
Á pulse Á nm,
respectively. As the U
AB
A i
ðkÞ, u
AB
i ðkÞ, the absolute quantum yield of luminescence is a function of a wavelength of exciting radiation, in general.
The definitions (4.1.18)–(4.1.26) differ fundamentally from those represented in
some monographs. Here, by the absolute quantum yields of primary processes
(products) are meant the yields measured at monochromatic radiation within the
wavelength interval k ± Dk, for which quantum yields are independent of
photolysis radiation wavelength, and within volume unit, where n hm (k) = const,
and not in the whole irradiated volume as in [9]. The remark above is essential
for the study of secondary processes, the rate of which may depend upon the
n hm (k), N hm (k).
5. The absolute integral quantum yield for i-th AB photodecay process within the
absorption band of AB is defined as follows. It is equal to the ratio of the area
r
AB
i
under the spectral curve of AB partial absorption cross-section, which leads
to the i-th process, to the total absorption cross-section area r AB (k) under the
spectral curve within the AB absorption band:
84
4 Photolysis of Free Molecules