1. INFRARED SPECTROSCOPY OF DISILICON-CARBIDE, Si2C
DANIEL WITSCH, VOLKER LUTTER, GUIDO W. FUCHS, THOMAS GIESEN
Institute of Physics, University of Kassel, Germany
JÜRGEN GAUSS,
Institut für Physikalische Chemie, Universität Mainz, Germany .
Talk WA07
72nd Meeting ISMS June 2017
Champaign-Urbana, Illinois

2. MOTIVATION Astrophysics: Physical Chemistry:
SinCm molecules are building blocks of interstellar dust grains
Radioastronomical detection of SiC, SiC2, Si2C, c-SiC3, SiC4 in shells of late-type star IRC+10216
ALMA revealed many U-lines in the dust forming region of IRC+10216
TEXES and EXES/SOFIA new high resolution instruments for the mid-IR
Physical Chemistry:
Vibrations, structures, chemical bonds of isovalent species SinC3-n, n ≤ 3
NEED OF MID-IR LABORATORY DATA

3. Microwave Spectra and Equilibrium Structure of Disilicon Carbide
M.C. McCarthy et al., J. Chem. Phys. Lett. 6, 2107 (2015)
Microwave Spectra and Equilibrium Structure of
Disilicon Carbide
(2) Å
(3)°
Discovery of Si2C with 30m-IRAM in IRC+10216
J. Cernicharo, M.C. McCarthy, C.A. Gottlieb et al., ApJ. Lett. 806, L3 (2015)
Electronic transitions of jet-cooled Silicon Carbides
Si2C
SiC2
M. Steglich, J. P. Maier, ApJ 801, 119 (2015)
Ground State Vibrational Structure of Si2C:
Dispersed Fluorescence Spectroscopy at 390 nm
N.J. Reilly et. al., J.Phys.Chem. 142, (2015)

4. Infrared Fundamental Modes and Relative Intensities
(b2)
INFRARED SPECTROSCOPY OF Si2C
J.D. Presilla-Marquez, W.R.M. Graham, J. Chem. Phys. 95, 5612 (1991)
Fourier transform vibrational spectroscopy of Si2C in solid Ar
Infrared Fundamental Modes and Relative Intensities
Obs. a)
Ar Matrix
Theor. b)
This c) work
anharm contr. c)
n1 (a1)
839.5
808
838.0
-17.25
0.07
0.084
n2 (a1)
(172)
131
142.7
-7.79 
0.01
0.004
n3 (b2)
1188.4
1223
1206.6
-15.94
1.00
1.000
a) J.D. Presilla-Marquez, W.R.M. Graham, JCP 95, 5612 (1991)
b) C. M. L. Rittby, JCP 95, 5609 (1991) MBPT2/6·311G(2d)
c) CCSD(T)/cc-pCVQZ

5. Infrared Supersonic Jet Spectrometer

9. Si2C ab initio A [MHz] B [MHz] C [MHz] Be 61361.1 4447.3 4146.7 Be-B0
4447.3 
4146.7 
Be-B0
41.4
36.7 BO
4405.9  
4110.0
alpha
68.1  
43.9
B1 (n3)
4474.0 
4153.9
n3 [cm-1]
1206.6
Geometry: CCSD(T)/basis-set limit+fc-CCSDT/TZ+fc-CCSDTQ/DZ+core/5Z
Vibration-rotation-constants and frequencies: CCSD(T)/cc-pCVQZ

10. Extended Spectral Range

11. Rotational Diagram of Si2C Emission Lines measured in IRC+10216
Rotational Diagram of Si2C Absorption Lines measured in a Supersonic Jet Expansion
J. Cernicharo, M.C. McCarthy, C.A. Gottlieb et al., ApJ. Lett. 806, L3 (2015)
Rotational Diagram of Si2C Emission Lines measured in IRC+10216
NJ /N(2J+1)

12. n3 (b2) Asymmetric Stretching Mode of Si2C at 1202 cm-1
Measured and Calculated Spectrum from best Fit Analysis

13. Pertubation of Ka´´=2 levels by Coriolis Interaction*
* N.J. Reilly et. al., J.Phys.Chem. 142, (2015)
Coriolis interaction term ξC = (26) cm-1

14. Pure Rotational Transitions up to 360 GHz

15. RESULTS

16. THANK YOU FOR YOUR ATTENTION !
CONCLUSIONS
First Infrared gas-phase spectrum of Si2C
Experimental results are in very good agreement with ab initio calculations
Precise IR-data for astronomical observations are now available
THANK YOU FOR YOUR ATTENTION !