1. HIGH RESOLUTION SPECTROSCOPY OF THE CARBON CAGE ADAMANTANE C10H16
Vincent BOUDON
Laboratoire Interdisciplinaire Carnot de Bourgogne – UMR 5209 CNRS-Université de Bourgogne, 9 Av. A. Savary, BP 47870, F DIJON, France
Olivier PIRALI*, Didier BALCON, Michel VERVLOET
Ligne AILES – Synchrotron SOLEIL, L’Orme des Merisiers, F-91192, GIF-SUR-YVETTE, France
* and ISMO, CNRS, Bat 210 Université Paris Sud, Orsay, France
Jos OOMENS
Inst. Plasma Phys. Rijnhuizen, FOM, NL-3439 MN Nieuwegein, Netherlands

2. Contents The adamantane molecule The spectra
Analysis of line positions
Conclusion

3. I. The adamantane molecule

4. Why adamantane ?
The simplest diamondoid molecule, composed of a single tetrahedral carbon cage.
Diamond-like molecules have unique structures and properties (stability, hadrness, rigidity, optical transparency, …).
Presence of diamond-like materials (which are more stable than graphite) is suspected in different astrophysical objects.
Intense emission features around 3.43 and 3.53 μm in the circumstellar shell of some Herbig objects to CH stretching modes of diamond-like molecules.
Such an identification remains hypothetical, however. Detailed spectroscopic studies of such molecules should be performed.

5. A tetrahedral cage
Calculated structure of C10H16 using the B3LYP DFT with the 6-31G(d,p) basis set.
There are 72 vibrational modes, including 11 F2 IR active modes.
The ground state rotational constant is estimated to:
B0 ≈ GHz
≈ cm-1

6. II. The spectra

7. AILES beamline at SOLEIL
High Resolution Absorption Spectroscopy in the Far-IR
Interferometer
Synchrotron beam entrance
Multipass cell :
Max = 200m
Bolometer detectors
Maximum spectral resolution = cm-1
Spectral range= cm-1

8. Overview of the vibrational spectrum

9. The high-resolution spectra
Different pressures have been used, because of band intensities ranging from a few tens to several hundreds of km.mol-1.
Spectral range / cm-1
Gaz pressure / mb
Spectral resolution / cm-1
Continuum source
Scan time / h
600 – 4500
0.02
0.001
Globar 40
33 – 600
0.07
Synchrotron 31
1000 – 2000
0.006 30
Optical path (White cell) : m

10. III. Analysis of line positions

11. Effective tensorial Hamiltonian
Polyad structure P0 P1 P2
Systematic tensorial development
Coupled rovibrational basis
Effective Hamiltonian and vibrational extrapolation

12. Overview of the n30 band

13. Detail in the n30 band

14. Detail in the n28 band

15. Detail in the n27 band

16. Detail in the n26 band

17. Rovibrational levles of the n26 band

18. Effective Hamiltonian parameters
At present, all the analyzed bands were considered as isolated.
Assignments could be realized up to high J values.
Many effective Hamiltonian parameters could be determined.

19. IV. Conclusion

20. A lot of work left The present analyses are still preliminary.
All bands were taken as isolated, but there may be interactions to consider.
A band is observed near 950 cm-1, just below ν27, which may be an interacting E level (probably ν11, observed in Raman).
ν27
ν11 ?
ν25 and ν24 could not yet be analyzed and may be perturbed.
Other bands may be recorded.

21. Spherical Top Data System
The STDS database
Spherical Top Data System
• Molecular parameter database
• Calculation and analysis programs
• XTDS : Java interface