Electronic Transitions

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Electronic Transitions
Fred J. Grieman
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Electronic Transition Selection Rules Term
symbol 2S1?O Product Wave Function ? ?e
?v ?r Dipole
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Electronic Part
?J 1, 0, -1 R Q P Except S-S
?J 1
re re lt?o?ogt Large lt?v ?vgt
Large lt?v?o ?ogt Small
re gt re lt?o?ogt Small lt?v ?vgt
Small lt?v?o ?ogt Large
?e strong progression
?e weak progression
I
I
E
E
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Spectrum Information derived from analysis E
Ee Ev Er Te G(v)
F(J,v) Electronic Transition ?E Te
Te G(v) G(v) F(J,v)
F(J,v) XTe 0 Te (M.O.s) ?e,
?exe, Be, De, ae
?e, ?exe
Be, De, ae Examples N2 I2
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Electronic Transitions in N2 and N2
Te (cm-1) ?e (cm-1) re
(Å) a 1Su- 68152.66 1530.25 1.2755 X
1Sg 0 2358.57 1.09768
su
N2
sg ? pg forbidden
pg
sg ? su pu ? pg allowed bonding to
antibonding orbital Spectrum found in the
ultraviolet
sg
pu
su
N2
su


-
pg
A2?u
X2Sg
B2Su
Te (cm-1) 9166.95
25461.46
sg
sg
sg
pu
pu
pu
su
su
su
re 1.116 Å
re 1.210 Å
re 1.075 Å
?e(cm-1) 2207.00
1903.70 2419.84
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N2
B
V 3 2 1 0
A
X
B ? X Weak Vibrational progression
Strong (0,0) band A ? X Strong
Vibrational progression Weak (0,0)
band
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I2 in Chem 162 Lab
su
su
pg
pg
pu
pu
sg
sg
su
su

• a3?u
• ? 0 (allowed even though ?S 0)
• Re 3.016Å

X 1?g ? undefined Re 2.666Å
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I2 Potential Energy Curves
I (2P1/2) I(2P3/2)
V 15-60
a3?u
I (2P3/2) I(2P3/2)
E
X 1?g
V 2 1 0
Re
? E