Chemistry Reference
In-Depth Information
3p
σ
u
C
2
H
2
C 1s
I
0
ν
1
3s
σ
g
ν
2
ν
2
3
σ
u*
I
90
3p
π
u
ν
2
ν
5
ν
1
ν
5
287.6
288.0
288.4
288.8
289.2
289.6
Photon Energy (eV)
Figure 10.
High-resolution ARPIS of C
2
H
2
in the 1s
→
3
σ
u
valence and 1s
→
3s and 3p
Rydberg excitation region. These states show vibrational fine structures.
emit H
+
ions to the bent direction? As indicated in Fig. 11, the 1s
σ
g
→
3
σ
u
(
1
u
)
1
π
g
(
1
u
) excited
state is not repulsive along the C-H bond. This finding means that the excita-
tion energies of these states are very close near the crossing point. Consequently,
the 3
σ
u
state could have a lower-energy bent conformation through the strong
vibronic coupling. Thus, it has a conical intersection at the crossing region, and
the
σ
∗
excited state in the perpendicular direction can also be observed through
cis bending [92, 98].
excited state is repulsive along the C-H bond, but the 1s
σ
u
→
V. ARPIS OF O
2
Oxygen molecule (O
2
) has two more electrons than N
2
, but the 1
π
g
orbital is not
3
σ
u
(B and C) excitations in O
2
as in N
2
. However, the ground state of O
2
is a triplet open
shell (
3
g
) and the ionized and excited states have exchange (EX) splittings for
1
π
g
fully occupied. In Fig. 12, we can observe both 1s
σ
u
→
(A) and 1s
σ
g
→
