Electronic Transition

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Electronic Transition
(????????????????????????????????)
Allowed Transition
Forbidden Transition
- Spin - Forbidden Transition - Symmetry -
Forbidden Transition
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Spin-Forbidden Transition
Selection Rules ??????? transition
??????????? ????????????????? Spin
multiplicity
???????????????????????????? ? ?????????????? unpa
ired spin ?????????????? 2S1
????? S ??? ?????????????????????????
3
???? spin multiplicity ???????????????????
???????? 2.1
electron spin (s)
?? ???? unpaired electron
spin multiplicity
Multiplicity
(2S1)
1
singlet
0
0 (
)
?
?
2
doublet
1 (
??? ?
)
?
?
3
triplet
1
2 (
??? ?
)
??
??
4
quartet
3 (
??? ?
)
???

???
4
???????????????????????????????
1. Singlet-Singlet Transition
- ?????????????????????????????????
????????????????? - fully spin allowed transition
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electron jump
ground state
Spin paired
SINGLET
Spin allowed Absorption
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electron jump
excited state
Spin paired
SINGLET
Spin allowed Fluorescence
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2. Triplet - Triplet Transition
-?????????????????????????????????
????????????????? - fully spin allowed transition
?????????????????????????????????????????
????????????????????????????????????????? S0
?????? T0
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- ???????????
??? ?????????????????????? ??????????????? ?
????????????????? ???????? ??????? Triplet
state ????????
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electron jump
Spin allowed Absorption
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3. Singlet - Triplet Transition
-?????????????????????????????????
??????????????????? - strongly forbidden
transition
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electron jump
spin trip
ground state
Spin paired
SINGLET
Spin forbidden Absorption
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electron jump
excited state
Spin Parallel
TRIPLET
Spin allowed Phosphorescence
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????????????????? ???????????? ?????? (spinning)
???? ???????????????
(angular momentum)
??????????????????????????? ??? magnetic moment
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?????????????????
spin 0
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??????? Singlet-Triplet transition
????????????????????? ?????????????????????????
?????????? spin ???????
(1/2) ??? -(1/2)
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?????????? ????????????? ???? ????
???????????????
1 2
- 1 2
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?????????????????????????????
??????????????????? ??????? total angular
momentum ?????
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Actual Singlet ??????? singlet (S)????????????
triplet ?????????? S S t
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Actual Triplet ??????? Triplet (T)????????????
singlet ?????????? T T s
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Pure triplet T
Pure singlet s
Actual Triplet State


hn
hn
(allowed)
hn
(allowed)
(forbidden)
(forbidden)
Actual Singlet State

t
S

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Symmetry-Forbidden Transition
????????????????????????????????????????????????
(dipole moment transition
mij)
mij 0
??????????????????????????????? (total forbidden)
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mij (Yi m Yj) dt
Yi ??? Yj ??? wave function ??????????????????
(i) ?????????????????????
(j) m ??? ??? dipole moment dt ??? ???
volume element (dt dx dy dz)
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??????????????????????????
????????? (excited state)
E2
DE hn E2 - E1
???????
????????? (ground state)
E1
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?????????????????????????????
4d
5s
4p
DE3
4s
3d
3p
3s
???????
2p
DE2
2s
DE1
1s
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Harmonic Oscillator ?????????????????????????????
?
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v5
v4
v3
????????????
v2
v1
v0 ? v1, v1 ? v2, v2 ? v3, ...
v0
req
???????????????????