Transcript NGUYEN_FB03.pptx

Extension of the Measurement, Assignment,
and Fit in the Ground State of the two-top
Molecule Methyl Acetate
Lam Nguyen and Isabelle Kleiner, Laboratoire
Interuniversitaire des Systèmes Atmosphériques (LISA)
S. Shipman, New College of Florida
K. Kobayashi, Toyama University
Lucy M. Ziurys and the ARO Staff, ALMA News from the
October 2006 Issue of the NRAO Newsletter
http://astro.goblack.de/Theorie/t_orion.htm.
L. E. Snyder, F. J. Lovas, D. M.Mehringer, N.Y. Miao, Y.-J. Kuan, J.M. Hollis, P. R. Jewell, Astrophys. J. 578, 245 (2002).
E. Herbst and E. F. van Dishoeck, Annu. Rev.
Astron. Astrophys. 2009, doi:
10.1146/annurev-astro-082708-101654
Internal rotation
AA AAE EA EE
E EE*
Frequency
Methyl acetate
• The smallest acetate ester
• Two internal rotors with
one low (100 cm-1) and one
intermediate barrier (400 cm1)
• Detection in interstellar
space of interest, but available
data before our work was not
yet sufficient.
100 cm-1
400 cm-1
Previous work
•
Sheridan and Bauder (1980):
• Stark spectrometers and microwave-microwave double
resonance
• Frequency range: 8 – 40 kHz
• About 100 lines, J  5 and K  3
Previous work
•
M. Tudorie et al. (2011):
• ≥ 800 new lines in the ground state, J  19 and K  7
• MBFT microwave spectrometer in Aachen (3-40
GHz): 315 lines, weighted to 4 kHz.
• Free jet absorption Stark-modulated millimeterwave spectrometer in Bologna (60-77 GHz): 519
lines, weighted to 40 kHz.
• Fit using the program BELGI-Cs-2tops written by I.
Kleiner , 27 molecular constants, 836 lines. All lines were
fitted to their measurement error.
Extension of the assignment and fit
• New spectroscopic data for methyl acetate
• Jet-cooled sub-millimeter wave data from K. Kobayashi,
Toyama (Japan), measurement error: 50 kHz.
• Room temperature Chirp-pulsed MW data from S.
Shipman, Florida (USA), measurement error: 80 kHz,
spectrum range from 8.7 to 27 GHz.
• New fit with BELGI-Cs-2tops using these data:
• Sub-mm wave lines: J  19 and K  9
• RT CPMW lines: J  30 and K  15
• 36 parameters were fitted. All new parameters are J, K
dependent parameters.
• All lines were fitted to their measurement errors.
Room temperature CPMW spectrum – why?
• Torsional excited state vt = 1, 2, 3…
are important to:
• Uncorrelate the
parameters
• Test the program by
handling the top-top
interaction problem
BELGI-Cs-2tops fit
• More than 1100 lines were included in the fit.
• 36 parameters were fitted. All new parameters are J, K
dependent parameters (V31J, V32J etc.).
• All lines were fitted to their measurement error.
• Extension of the measurement, assignment, and fit of
the ground state of methyl acetate is a necessary step
before searching for vt = 1 transitions in both torsional
modes in the room temperature spectrum.
• The ground state data with higher J and K are getting
more precise and useful for astrophysics.
Conclusion
• Over 1100 methyl acetate lines in the torsional ground state
with J  30 and K  15 were fitted using the program BELGICs-2tops to experimental accuracy with 36 parameters.
• Methyl acetate was detected in the interstellar space using
these improved parameters.
Outlook
• Extension of the assignment and fit to J  50 in the ground
state.
• Begin searching for vt = 1 transitions in the RT CPMW
spectrum.
Acknowledgement
• PROCOPE
(travelling)
• ANR "TopModel"
contract