Transcript water.ppt

Analysis of new data sets pertaining
to the water molecule
a
a
a
S. Yu, J. C. Pearson, B. J. Drouin, H. S. P. Müller,
b
c
c
S. Brünken, M. A. Martin-Drumel, O. Pirali,
c
d
D. Balcon, and L. H. Coudert
a
b
JPL, California Institute of Technology, Pasadena, USA
b
Physikalisches Institut, Universität zu Köln, Köln, Germany
c
Ligne Ailes – Synchrotron Soleil, L'orme des Merisiers, Gif-sur-Yvette, France
d
LISA, CNRS/Universités Paris Est et Denis Diderot, Créteil, France
Why are we interested in water?
Determining accurately the abundance of water in the ISM is an
important issue. There are biological implications.
1
Since the first detection of water in the 22 GHz region, a large
number of transitions have been measured in the lab up to 5 THz.
Accurate FIR transitions involving high-lying rotational levels have
been measured.
This work aims at building an accurate line list for the water
molecule up to 5 THz.
1. Cheung, Rank, Townes, Thornton, and Welch, Nature 221 (1969) 626.
Outline
• The new microwave data
• Experimental setup used at JPL and in Cologne
• The new FIR data
• Experimental setup
• The line position analysis
• Results for the microwave data
• Results for the FIR data
• Conclusion
The new microwave data
169 transitions measured at JPL
Frequencies range from 325 GHz to 2.72 THz
Highest level involved is the 927 (001) level at 4940 cm-1
55 transitions measured in Cologne
Frequencies range from 293 GHz to 2 THz
Highest level involved is the 1349 (100) level at 6149 cm-1
622 frequencies available now for water.
Many measurements are redundant.
The JPL experimental setup
H2O
Pump
Sample cell
Beamsplitter
Rooftop
reflector
Si detector
Lock-in
PC
×3
…
×2
Discharge
×6
FM
Multiplier chain
Rf Synthesizer
Source frequency: 300–1230, 1575–1626, 2480–2750 GHz
H2O: ~100 mTorr
Discharge cell: 1.2-meter-long
DC discharge: 200 mA, ~4.5 kV
Observed 2.6 THz H2O lines at JPL
E" = 3479 cm-1
E" = 1921 cm-1
E" = 4407 cm-1
Absorption peak is up with out phase convention
The experiment in Cologne
• Frequency range
– 290–968 GHz with BWOs
– 1.42–1.45 THz with a VDI multiplier chain
– 1.85–1.99 THz with a sideband spectrometer
• Numerous ways to generate hot water
– RF discharge (200 W, ~2 m)
– DC discharge (~2 kV, ~300 mA and 1.5 m)
– A pyrolysis oven (~1500 K and 50 cm absorption path)
– Heating tape (~450 K and 3.5 m)
• Pressures: 10–50 mTorr
• Detector: a composite InSb bolometer cooled with liquid He
Observed frequency inconsistencies
J' Ka' Kc' V' J" Ka" Kc" V"
Obs. Freq.
Unc.
17
4 13
0 16
7
10
0
354808.4140
0.200
Cologne 2010
17
4 13
0 16
7
10
0
354808.5800
0.200
Amano et al 1991, CPL 182, 96
17
4 13
0 16
7
10
0
354808.8770
0.150
Pearson et al 1991, APJ 379, L41
6
3
3
1
5
4
2
1
926187.4750
0.253
Matsushima et al 2006, JMS 235, 190
6
3
3
1
5
4
2
1
926187.8120
0.100
Cologne2010
6
3
3
1
5
4
2
1
926187.8470
0.050
JPL2009
1
1
1
1
0
0
0
1
1205788.6400
0.250
Chen et al 2000, APJS 128, 371
1
1
1
1
0
0
0
1
1205788.8360
0.257
Matsushima et al 2006, JMS 235, 190
1
1
1
1
0
0
0
1
1205789.0950
0.075
JPL2009
2
2
0
1
2
1
1
1
1494057.1540
0.250
Chen et al 2000, APJS 128, 371
2
2
0
1
2
1
1
1
1494057.5420
0.050
Cologne2010
2
2
0
1
2
1
1
1
1494057.7170
0.170
Matsushima et al 2006, JMS 235, 190
6
2
4
1
5
3
3
1
2541727.7980
0.180
Matsushima et al 2006, JMS 235, 190
6
2
4
1
5
3
3
1
2541728.0110
0.100
JPL2010
6
2
4
1
5
3
3
1
2541728.0163
0.100
JPL2011 with discharge
The new FIR data
Fourier transform IFS 125 Bruker interferometer of the Ailes beam line at Soleil
1000 Watt radio frequency discharge1 working at 13.6 MHz
Rotational temperature around 1500 K
1. Pirali and Vervloet, Chem. Phys. Letters 423 (2006) 376.
A small portion of the FIR spectrum
Emission spectrum
The measured FIR transitions
3767 transitions assigned.
Transitions within higher lying states have also been assigned.1
1. Martin, Pirali, Balcon, Vervloet, and Coudert, TE04, Columbus (2010)
The line position analysis
The data available up to the first triad were
fitted in addition to the microwave and FIR data.
The anomalous centrifugal distortion has been
accounted for using the bending-rotation
approach.1-8
1. J. Mol. Spec. 154 (1992) 427. 2. J. Mol. Spec. 165 (1994) 406. 3. J. Mol. Spec. 181 (1997) 246.
4. J. Mol. Spec. 195 (1999) 54. 5. Mol. Phys. 96 (1999) 941. 6. J. Mol. Spec. 206 (2001) 83.
7. J. Mol. Spec. 228 (2004) 471. 8. J. Mol. Spec. 251 (2008) 339.
Results
Microwave transitions with a very small experimental
uncertainty (< 50 kHz) are difficult to reproduce.
The effects of frequency shift due to pressure and temperature are
not very well known.
A portion of the O-C table
Residuals for the FIR data: this work
Residuals for the FIR data: Hitran
Only 1048 transitions found out of 3767.
Residuals for the FIR data: BT2
Final results
Intensities will be calculated from
the previous investigations.