[mahyar310]

I used several methods to get the electron structure of ¹Σ⁺_g singlet oxygen (second excited state) in Gaussian09 or Jaguar9.8 (Schrodinger suites), for example

# opt ucis=(singlets,root=2)/6-31+g(d,p)
singlet sigma+g oxygen
0 1
O 0.00000000 0.00000000 0.70417356
O 0.00000000 0.00000000 -0.70417356

But the results are ¹Δ_g singlet oxygen (first excited state)?
https://en.wikipedia.org/wiki/Singlet_oxygen

or

# opt casscf(6,6,nroot=X)/6-31+g(d,p)
Title
0 1
O 0.00000000 0.00000000 0.60287642
O 0.00000000 0.00000000 -0.60287642

when X=1 or casscf(6,6)
Final one electron symbolic density matrix:
1 0.194995D+01 =π₁ with two electron
2 0.194995D+01=π₂ with two electron
3 0.104995D+01 = π^*₁ with one electron
4 0.104995D+01= π^*₂ with one electron
5 0.902987D-04 = σ ^*empty
6 0.119828D-03 = Empty
when X=2
Final one electron symbolic density matrix:
1 0.192295D+01
2 0.192295D+01
3 0.107694D+01
4 0.107694D+01
5 0.873522D-04
6 0.121063D-03
when X=3
Final one electron symbolic density matrix:
1 0.189273D+01
2 0.189273D+01
3 0.110413D+01
4 0.110413D+01
5 0.128968D-03
6 0.615265D-02

All three states are the same???! all are ¹Σ⁺_g

http://www.molpro.net/pipermail/molpro-user/2009-September/003319.html