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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
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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
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Low-resolution LIF spectrum
vibronic bands for the 2Du–2Pg system vibronic bands with shorter lifetimes (c. a. 50 ns)
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Ab initio calculations
MRSDCI+Q / cc-pVTZ (9e in 9o) X 2Pg 7sg 3pu 2pg 5su 12Pu D 2Sg+ C 2Du
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High-resolution LIF spectrum
G. S. of the observed bands are that of SiNSi P–P and S–P type vibronic bands were observed
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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
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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
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Rotational constants for the D2Sg+ state
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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).
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Low-resolution DF spectra
C 2Du → X 2Pg D 2Sg+ → X 2Pg
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High-resolution DF spectra
(030)Pu pumped (010)Pu pumped
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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
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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
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Low-resolution LIF spectrum in the visible
arrows indicate bands containing Si and N atoms
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DF spectra from the visible bands
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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
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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.
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