a) 1Σ+ <-> 1Σ+u
b) 3Σ+g <-> 3Σ+u
c) t2g <-> eg
d) π* <-> n
If it is possible, please explain to me exactly how to do it because I am very lost. I will give best answer quickly. Thank you.
b) 3Σ+g <-> 3Σ+u
c) t2g <-> eg
d) π* <-> n
If it is possible, please explain to me exactly how to do it because I am very lost. I will give best answer quickly. Thank you.
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First, you have to know the molecular term symbol formula. It has the general formula:
(2S+1)Λ(+/-) Ω,(g/u)
S = total spin quantum number. +1/2 for spin up and -1/2 for spin down.
Λ = orbital angular momentum. Similar to the L value of conventional term symbols. With regular term symbols, you use:
. . .S P D F. . .
L = 0, 1, 2, 3. . .
For Λ, you use Greek alphabets (for whatever reason):
L = 0, 1, 2, 3. . .
Λ = Σ, π, Δ, ϕ. . .
Ω = total angular momentum. Similar to the J value of regular term symbols.
g/u = parity. It is either g or u. This depends on its inversion state. If it changes at all, it's u. If it doesn't change, then it's g. It is only included for diatomic molecules.
+/- = reflection symmetry along internuclear axis.
The allowed transitions are:
ΔΛ = 0, ±1
ΔS = 0
ΔΩ = 0, ±1
Parity = g -> u or u -> g
a) I think you are missing parity. Is it 1Σ+u <-> 1Σ+u or 1Σ+g <-> 1Σ+u? If it is the first one, then it is forbidden, because the parities is u->u, which is not allowed. It is allowed if the second one, because the parities change, and everything else is fine.
b) It is allowed.
c) Electronically allowed.
d) π* is an anti-bonding orbital, and n is a non-bonding orbital. You can go from non-bonding to anti-bonding, but you cannot go from anti-bonding to non-bonding. So it is forbidden.
(2S+1)Λ(+/-) Ω,(g/u)
S = total spin quantum number. +1/2 for spin up and -1/2 for spin down.
Λ = orbital angular momentum. Similar to the L value of conventional term symbols. With regular term symbols, you use:
. . .S P D F. . .
L = 0, 1, 2, 3. . .
For Λ, you use Greek alphabets (for whatever reason):
L = 0, 1, 2, 3. . .
Λ = Σ, π, Δ, ϕ. . .
Ω = total angular momentum. Similar to the J value of regular term symbols.
g/u = parity. It is either g or u. This depends on its inversion state. If it changes at all, it's u. If it doesn't change, then it's g. It is only included for diatomic molecules.
+/- = reflection symmetry along internuclear axis.
The allowed transitions are:
ΔΛ = 0, ±1
ΔS = 0
ΔΩ = 0, ±1
Parity = g -> u or u -> g
a) I think you are missing parity. Is it 1Σ+u <-> 1Σ+u or 1Σ+g <-> 1Σ+u? If it is the first one, then it is forbidden, because the parities is u->u, which is not allowed. It is allowed if the second one, because the parities change, and everything else is fine.
b) It is allowed.
c) Electronically allowed.
d) π* is an anti-bonding orbital, and n is a non-bonding orbital. You can go from non-bonding to anti-bonding, but you cannot go from anti-bonding to non-bonding. So it is forbidden.