1. Fourier-Transform absorption spectroscopy of C3 in the 3 antisymmetric stretch mode region
M. VERVLOET, M. A. MARTIN-DRUMEL., D. W. TOKARYK, O. PIRALI
ISMO, CNRS-Universite Paris-Saclay, Orsay, France
AILES beamline, Synchrotron SOLEIL, Saint-Aubin, France
Department of Physics, University of New Brunswick, Fredericton, NB, Canada

2. Objective: record the (0,n2l,1) - (0,n2l,0) transitions
Context
C3 is a linear, symmetric molecule
4050 Å band from comet spectra first seen in 1882; assigned to C3 by Douglas (1951)
Gausset et al. (1965) studied the A 1Пu – X 1Σg+ electronic system – the analysis revealed a
large Renner Teller splitting in the A 1Пu state and low energy (about 65 cm-1) of the X 1Σg+ 2 bending state
3 vib modes (1, 2l, 3), 2 and 3 and IR active: diode laser spectroscopy of the 3 band by Kawaguchi et al, J. Chem. Phys, 91 (1989) and 2 band by Schmuttenmaer et al. 1990
Lines of the 3 band of C3 detected in the circumstellar envelopes (Hinkle et al., Science 1988) and absorption lines of 2 band (Giesen et al., ApJ 2001)
Objective: record the (0,n2l,1) - (0,n2l,0) transitions

3. Experimental set-up on the AILES beamline of SOLEIL
Electrical DC discharge coupled to the FT
24 m absorption pathlength
Resolution = 100MHz (0.004 cm-1)
Discharge : ~ 1KV / 1A
Gas mixture : CH4 seeded in 1 mbar He
Intense lines are due to CO

4. Comparison with diode laser spectrum: (0,n2l,1) - (0,n2l,0)
(0,2,0)
P(40)
(0,2,0)
R(13)
R(14)
(0,1,0)
P(7)
(0,1,0) 
P(6)
Kawaguchi et al. (1989)
(0,0,0)
P(40)
Wavenumbers (cm-1)

5. Stimulated Emission Pumping
Data from electronic transitions to support our analysis
In addition to IR data (Kawaguchi et al., Krieg et al.) and ab-initio calculations (Per Jensen)
Analysis of the 4050 Ǻ group :
A 1Пu – X 1Σg+, L. Gausset et al. Astrophys. J. 142, 45 (1965)
(000) , (010), (020), (020), (030) , (040) 
Stimulated Emission Pumping
- Nothrup and Sears
(0,2n 2,0) states with l= 0 (), 2 ()
Rohlfing and Goldsmith
(0, 2n+1 2, 1) states with l=1 ()

6. Spectral analysis procedure and effective Hamiltonian
J-1
R(J-1) J
J+1
P(J+1)
F2(J) for the lower state = R(J-1)-P(J+1)
R(J)
P(J)
F2(J) for the lower state = R(J)-P(J)
(0, 2,1)
(0, 2,1)
USCD
(0, 2,0)
LSCD
(0, 2,0)
Formulation from Maki et al, J. Mol. Spec. 36, (1970) includes the l-type resonance
< J,v,l|H|J,v,l > = Bv[J(J+1) - l2] -Dv [J(J+1) - l2]2 + Hv[J(J+1) - l2]3
< J,v,l|H|J,v,l ± 2> = (1/4)q[(v l)(v ± l + 2]½ {[J(J+1)-l(l ±1)] [J(J+1) – (l ± 1)(l ± 2}½
q → q +qjJ(J+1) + qjjJ2(J+1)2

7. Analysis (021)-(020); (021) - (020)
Extension of Kawaguchi et al observations up to J=55
Plots of the 2(J) for (0,2,1)  states shows a local perturbation for J=33-34.
Proposition of (190)  state as the perturber level. Based on SEP data from Northrup and Sears who observed (180)  at 1993 cm-1
2(J)
J(J+1)

8. Analysis of (041) - (040) ; (041) - (040); (041) - (040)
Gausset et al. provide term values for (040) state.
Northrup and Sears provide low J combination differences for the (040) state
Lines involving (040) are more intense than the l=0 and 2 and the l-doubling effect is weaker
Analysis of (041) - (040)  band rely on the model and fit. 41 lines f levels, Jmax=45 Ev
B/cm-1
D/10-5 cm-1
H/10-9 cm-1
q/10-2 cm-1
qJ/10-6 cm-1
(0,4,0) Σ
286.52
(30)
0.2744(38)
0.133(14)
0.4885(8)
(31)
(0,4,0) Δ
(10)
(26)
0.2929(27)
0.181(9)
(0,4,0) Γ
(11)
(23)
0.3369(25)
0.200(8) Ev
B/cm-1
D/10-5 cm-1
H/10-9 cm-1
q/10-2 cm-1
qJ/10-6 cm-1
(0,4,1) Σ
(18)
(28)
0.3130(37)
0.109(14)
0.5706(8)
(30)
(0,4,1) Δ
(97)
(24)
0.3704(26)
0.214(9)
(0,4,1) Γ
(11)
(23)
0.5116(25)
0.369(8)
200 lines (, ,  states); RMS of the fit about cm-1 (exp accuracy about cm-1)

9. Summary
(050)
R(31)
R(33)
(050)
R(34)
(040)
R(18)
(040)
R(21)
R(23)
(040) 
(040)
R(27)
R(26)
(030)
R(8)
R(9)
(030)
R(14)
R(16)
R(15)
Extension of the analysis to bands involving higher quanta of 2
Comparison with recent theoretical calculations (Schröder and Sebald, J. Chem. Phys 2016)
We plan to analyse our data using semi-rigid bender approach (S. Ross, UNB)

10. Atlas of Comet 122P/de Vico: Cochran and Cochran, Icarus 2002
C3 in cometary spectra: « 4050 Å group » : A1u – X1g+ (Gausset el al and Merer 1967)
Span from 3350 Å to 4700 Å

11. Atlas of Comet 122P/de Vico: Cochran and Cochran, Icarus 2002
Пu – Σg+
Пu – Σg+
Пu – Σg+
Пu – Δg
Пu- – Σg+
Пu- – Σg+
Пu+ – Σg
Пu+ – Σg
Пu+ – Δg
Пu+ – Σg
Пu+ – Δg
Пu- – Σg+
Пu- – Σ
Пu – Σg+
Δg – Пu
Δg – Пu
Σg- – Пu
Σg- – Пu
Σg+ – Пu
Σg+ – Пu
Σg- – Пu

12. Atlas of Comet 122P/de Vico: Cochran and Cochran, Icarus 2002
Identification of 16 U lines all shifted by 0.3 cm-1 in comparison to lab data
8 for Σg- – Пu
8 for Σg+ – Пu
Due to uncertainty of the energy of (051) that we use to determine (050) involved in the cometary band (about 0.5 cm-1)
Gausset
A (010)
Rohlfing
X (051)
X (050)
X (000)
THANK YOU!