1. LASER INDUCED FLUORESCENCE SPECTROSCOPY OF THE SiNSi RADICAL II: IDENTIFICATIONS OF THE A2A1, B2B1, AND D2Sg+ STATES
C. MOTOYOSHI, Y. SUMIYOSHI, Y. ENDO
Department of Basic Science, The University of Tokyo, Tokyo , Japan
M. FUKUSHIMA, T. ISHIWATA
Faculty of Information Sciences, Hiroshima City University, Hiroshima , Japan

2. Background of the Study
Observation of LIF spectra of species containing Si and N in the near UV region　(30,000 – 34,000 cm–1)
Assigned the species to be linear SiNSi for the 2Du – 2Pg system (previous talk)
However, there remained more vibronic bands, which could not be assigend to the 2Du – 2Pg system

3. Low-resolution LIF spectrum
vibronic bands for the 2Du–2Pg system
vibronic bands with shorter lifetimes (c. a. 50 ns)

4. Ab initio calculations
MRSDCI+Q / cc-pVTZ (9e in 9o)
X 2Pg
7sg
3pu
2pg
5su
12Pu
D 2Sg+
C 2Du

5. High-resolution LIF spectrum
G. S. of the observed bands are that of SiNSi
P–P and S–P type vibronic bands were observed

6. Constants for the new bands
(cm-1) Pu Tv
(1)
(9) DE
226.45
Aveff
Bveff
(4)
(2)
104 qv
- 2.2(1)
- 4.85(4) s
0.008
0.007
unresolved spin components
⇒ vibronic P levels of a S electronic state
Su+ Tv
(1)
(1)
(2) DE
839.12
Bveff
(2)
(3)
(3) s
0.009
0.007
0.021

7. The D2Sg+ state predicted Te = 31300 cm-1
32400
Su+
(101)
predicted Te = cm-1
vibronically allowed transitions
(only u vibronic levels are seen)
Forbidden due to centro-symmetry (g/u)
+n1(Sg)
Su+
(021)
32000
31800
Su+
(001)
+n3(Su) Fu
31200
(030) Pu Dg
(020)
Sg+
31000 Pu
(010)
Sg+
(000)
30800

8. Rotational constants for the D2Sg+ state

9. Vibrational analysis for the D2Sg+ state
All vibronic energies are reproduced within 1 cm–1 Te w1 w2 w3
x22 s
(cm-1)
29828(2)
608.0(5)
148(2)
959.6(7)
- 5.8(3)
0.65 Be a1 a2 a3 s
(cm-1)
0.1132(2)
0 (fixed)
(4)
(9)
The D 2Sg+ state has shallower bending potential curve than that of the C 2Du state (w2 = 233 cm-1).

10. Low-resolution DF spectra
C 2Du → X 2Pg
D 2Sg+ → X 2Pg

11. High-resolution DF spectra
(030)Pu pumped
(010)Pu pumped

12. Observation of the A2A1 and B2B1 states
Fluorescence
D(010)
pump
12Pu
B 2B1
A2A1
D(030)
A 2A1
Linear
The energy at the linear geometry (12Pu) is estimated to be cm–1

13. Potential energies for the A2A1 and B2B1 states
MRSDCI+Q / cc-pVTZ (11e in 9o)
B2B1
B 2B1
A 2A1
2B2
A2A1
X 2Pg
2A2
Ornellas and Iwata, J. Phys. Chem. 100, (1996)
low lying bent isomer

14. Low-resolution LIF spectrum in the visible
arrows indicate bands containing Si and N atoms

15. DF spectra from the visible bands

16. Analysis of the ground vibronic state
Observed levels when the cm-1 band was pumped (in cm-1)
Level
o.–c.
Assignment
(000)P1/2
838
- 0.2
(060)mP1/2
140
- 1.8
(000)P3/2
- 1.3
(060)mP3/2
268 – ?
874
285
- 3.4
(020)mP1/2
1039
2.9
(040)kP3/2
310
1.0
(020)mP3/2
1055
3.8
(040)kP1/2
534
1.3
(040)mP3/2
1118
1.8
(080)mP1/2
557
- 2.2
(040)mP1/2
1134
3.1
605
- 2.8
(020)kP1/2
1389
- 3.5
(080)mP3/2
631
2.5
(020)kP3/2
1505
- 3.7
(060)kP1/2
Newly obsered
Analyzed using the RT3 program (He and Clouthier, CPC 178, 676 (2008))
The determined parameters for the ground state w2 e
ASO s
(cm-1)
187.8(3)
0.48(9)
155(2)
2.8

17. Conclusions
A new band system, D2Sg+, has been assigned, which becomes allowed by the vibronic coupling.
Dispersed fluorescence spectra from the D state showed new electronic states, which were assigned to states with bent structures (A2A1 and B2B1 states).
Low-resolution LIF spectrum for the visible system was observed.
Dispersed fluorescences to higher vibronic levels for the ground state have been observed by exciting this system.