Transcript Columbus_talk_sildes _set M_June-2012.pptx

LINE PARAMETERS OF THE PH3 PENTAD IN
THE 4-5 µm REGION
V. MALATHY DEVI and D. CHRIS BENNER
College of William and Mary
I.KLEINER
CNRS/IPSL-Universites Paris-ESt and Diderot, France
R. L. SAMS and T. A. BLAKE
Pacific Northwest National Laboratory
L. R. BROWN
Jet Propulsion Laboratory
L. N. FLETCHER
Department of Physics, University of Oxford
Overview
Why are we interested in PH3 pentad?
Previous studies and energy levels
Resonances & interactions in the pentad
Experimental conditions & sample spectra
Preliminary results on Position and Intensity fits
Line shapes (widths, shifts, line mixing & speed
dependence)
widths vs. J and K
Empirical fits for widths
Comparison of widths in n1 & n3 to n2 & n4
Conclusions and acknowledgments
Phosphine is a molecule of astrophysical and astronomical
interest. It has been observed on both the Jupiter and Saturn
• It is a symmetric top molecule with a pyramidal structure; has 4
IR fundamental vibrational bands, n1, n2, n3 and n4.
• The most prominent absorption features in the pentad are the two
strong overlapping bands n1 and n3 located at 2321.131 and
2326.877 cm-1.
• The other 3 bands in the pentad (2n2, n2+ n4, and 2n4) are weak
and are located on the lower wavenumber side.
• The complicated rotational structures of the n1 and n3 give rise to
strong Coriolis-type interaction between them. Other types of
anharmonic interactions also occur among the various bands.
• The Coriolis interaction gives rise to many “forbidden”
transitions and also results in large A+A- splittings.
The pentad region is revisited; because
• Accurate knowledge of line parameters for PH3 is important for Cassini/VIMS
exploration of Saturn and for correct interpretation of Jovian observations by
JUNO and ESA′s newly-selected mission, JUICE.
• A puzzling inconsistency in the mixing ratio derivations of PH3 with altitude
from Cassini VIMS and Cassini CIRS experiments were noticed by astronomers
and attributed it to the poor knowledge of PH3 spectroscopy in the pentad.
• Line parameters (e.g. positions and intensities) for all five bands in the 19302440 cm-1 are measured to improve the spectroscopic database for remote
sensing of the giant planets.
• Analysis of high resolution, high S/N spectra of high purity PH3 recorded with
the Bruker FTS at PNNL and the McMath-Pierce FTS on Kitt Peak are made.
• The strong n1 and n3 bands are recorded using very short absorption path cells
(~ 1.05 cm).
A brief survey of earlier studies is outlined next
PRIOR STUDIES OF PH3 (n and S) IN THE PENTAD
Band
Parameter
Investigators
n1 and n3
Rovibrational and
relative intensities
Baldacci et al.
n1 and n3
Line Intensities, few
line widths
Lovejoy et al.
2n2 , n2+n4
Rovibrational
Constants
2n2 , n2+n4,
2n4, n1, n3
Instrument or
data used
Grating
Spectrometer
Resolution
(cm-1)
Year
0.025-0.035
1980
Tunable diode
laser
Doppler
limited
1985
Tipton et al.
FTS
0.01
1986
Pentad, Theoretical
Modeling
Tarrago et al.
Using FTS data
0.0054
1990
2n2 , n2+n4,
2n4, n1, n3
Positions and int.
(line-by-line
simulation)
Tarrago et al.
FTS
0.0054
1992
n1, n3, 2n4,
n2+n4
Assignments and
A+A- splittings
Ulenikov et al.
FTS
0.005
2002
n1 and n3
Line intensities
Suarez
FTS
0.002
2002
n1, n3, 2n4,
n2+n4
HITRAN 2000
update
Kleiner et al.
Tarrago et al. line
parameters
0.0054
2003
n1, n3, 2n4,n2+n4
Line Intensities
Wang et al.
FTS
0.005
2005
dyad, pentad,
octad
Global Modeling
Nikitin et al.
FTS data from
various sources
0.002-0.0115
2009
Development of the theoretical model and new programs
G. Tarrago et al., J. Mol. Spectrosc.1990
2n2
2n2
n2+n4
2n42
n1
n3
K-type
interaction
Diag
n2+n4
l4
2n4
l4
n1
n3
l3
Coriolis
Coriolis
Fermi
Fermi
Coriolis
l- type
interaction
Diag
Coriolis
Fermi
Coriolis
l- type
interaction
Diag
Coriolis
Fermi
Coriolis
Fermi
K-type
Interaction
Diag
Coriolis
Fermi
l- type
interaction
Diag
Previous studies (not exhaustive)
• The Octad: The 8 vibrational bands shown on the left
Line positions at low resolution
(Maki et al., J Chem Phys, 1973)
Line positions and intensities, high resolution
(Butler et al., J Mol Spectrosc, 2006)
A Global analysis of the dyad, pentad and octad
(Nikitin et al., J Mol Spectrosc, 2009)
• The pentad (middle left): 2n2, n2+n4, 2n4, n1, n3 bands
Line Positions: fit to an rms=0.009 cm-1 up to J=16
(Tarrago et al., J Mol Spectrosc, 1992,
Ulenikov et al., J Mol Spectrosc, 2002)
Intensities: modeled to an rms.= 13%
(Tarrago et al., J Mol Spectrosc, 1992)
•The dyad (bottom left): n2, n4 bands
Line Positions: fit to an rms.=0.0004 cm-1 up to J=22
(Fusina et al., J Mol Struct, 2000). Intensities: rms.=2%
(L.R. Brown et al., J Mol Spectrosc, 2002)
Lorentz self-broadened width coefficients
(J. Salem et al., J Mol Spectrosc, 2004)
Experimental conditions of PNNL and Kitt Peak spectra, two
illustrative spectra recorded at PNNL
Bruker FTS at PNNL at 0.0022 cm-1
T = 298.2 K; Path length = 1.045 cm
McMath-Pierce FTS at 0.0115 cm-1
T= 289-294 K; Path length=425 cm
Sample Pressures (Torr)
2.048 4.24 10.152 22.46 50.11
Spectra were used for n1, n3, 2n4 and n2+n4
Sample Pressures (Torr)
1.50 3.72 3.16 6.30
Spectra were used for the weak 2n2
mm
5 room temperature spectra
with the PNNL FTS were fit
simultaneously using the
multispectrum fitting technique
3-4 Kitt Peak FTS were fit by
single spectrum fitting
technique for 2n2 transitions
Top left (RED): 4.24 Torr
Bottom left (Blue):22.46 Torr
Preliminary Energy Fit Results and a comparison
BAND
n0 (cm-1)
# lines
rms (cm-1)
Nikitin et al., 2009
2n2
1972.578
168
0.0033
172
0.0011
n2+n4
2108.185
631
0.0027
657
0.0018
2n4, l=0
2226.835
352
0.0034
415
0.0011
2n4, l=±2
2234.835
644
0.0034
657
0.0015
n1
2321.124
384
0.0030
454
0.0017
n3
2326.797
812
0.0031
980
0.0018
3287 line positions, up to J=14
67 floated parameters for the
upper states; GS constants: fixed
Global fit:
gs, dyad, pentad, octad
For the pentad:
374 fixed parameters
144 floated parameters
INTENSITIY FITS
1308 line intensities are fit with 19 adjustable
parameters; 6 leading terms of the dipole moment
derivatives and 13 Herman-Wallis terms
Band
# lines
rms(%)
2n2
120
6.9
n2+n4
391
10.4
2n4 (l = 0)
141
10.2
2n4 (l = 2)
165
10.1
n1
159
9.2
n3
332
8.0
The higher pressure spectra allowed us to measure
self-width and self-shift coefficients
Black: 2.048
Torr
Red: 4.24
Torr
Blue:10.152
Torr
Pink: 22. 46
Torr
Green: 50.11
Torr
n1
n2
 0
 T0 
 T0  
0
bL ( p, T )  p bL (Gas)( p0 , T0 )(1   )    bL ( self )( p0 , T0 )    
T 
 T  

0
0
n  n 0  p (Gas)(1   )   ( self )  
 0 (T )   0 (T0 )   (T  T0 )
Some of the A+A- pairs of lines exhibited Line Mixing.
A non Voigt line shape including line mixing and speed
dependence was used to fit the data.
Line mixing was
measured applying the off
diagonal relaxation matrix
formalism, e.g.;
[12C16O results: V. Malathy
Devi et al., JQSRT 113 (2012)
1013-1033]
Line 1 at 2218.38533(1) cm-1
Line 2 at 2218.42965(1) cm-1
PP(13,9)
pair K″=9 splitting
Self line mixing: 0.0291 (4)
cm-1 atm-1 at 296 K
LORENTZ SELF-BROADENED WIDTH
COEFFICIENTS IN THE n3 BAND OF PH3
Self-broadened width
coefficients (cm-1 atm-1 at
296 K) vs. Jm and Km
The term 0.05*(Jm-Km)
helps trend recognition
Jm and Km are max. J and
K
(a) Width vs. Jm for each
Km
(b) Width vs. Km for each
Jm
Where no error bars are
visible, the errors are smaller
then the font size used
EMPIRICAL POLYNOMIAL FITS FOR SELF WIDTHS IN THE n3 BAND
LEFT PANELS: ALL TRANSITIONS EXCEPT J=K
RIGHT PANEL: ONLY J=K LINES
Left: (a) Widths vs. Jm and (b)
Widths vs. Km (all lines except J=K )
Top: ONLY J=K LINES
The term 0.5* (Jm-Km) is used for
trend recognition
Comparisons of widths in the n1 and n3 bands [PS] to the n2 and n4 bands
[Salem et al. J. Mol. Spectrosc. 223 (2004) 174-181]
Transition J” K”
QR
QR
QR
QR
QR
QR
QR
QR
QR
QR
QR
2
2
7
7
7
7
9
10
10
12
12
Band [PS]
Widtha [PS]
Band [Salem et al.]
Width (SDRP) a,b
Ratio; [PS/Salem et al.]
n1
n1
n1
n1
n1
n1
n1
n1
n1
n1
n1
0.1105(3)
0.1100(2)
0.1085(2)
0.1057(2)
0.1073(2)
0.1052(2)
0.1022(2)
0.1009(3)
0.1047(12)
0.0965(5)
0.0882(19)
n2
n2
n2
n2
n2
n2
n2
n2
n2
n2
n2
0.1121(46)
0.1103(27)
0.1102(29)
0.1070(29)
0.1079(41)
0.0995(34)
0.1044(24)
0.1014(27)
0.0988(23)
0.0994(37)
0.0945(28)
0.986±0.041
0.997±0.024
0.985±0.026
0.988±0.027
0.994±0.038
1.057±0.037
0.979±0.023
0.995±0.027
1.056±0.027
0.971±0.036
0.933±0.034
0
1
0
1
2
5
4
2
7
2
9
Mean & std. dev. 0.995±0.036
PP 3 1
RP 4 1
RP 6 1
RP 7 0
PP 7 4
PP 8 5
RP 10 1
PP 11 11
a Units
n3
n3
n3
n3
n3
n3
n3
n3
are cm-1 atm-1 at 298.2 K;
0.1131(1)
0.1132(2)
0.1169(2)
0.1111(1)
0.1071(1)
0.1060(1)
0.1042(2)
0.0736(1)
b Speed-Dependent
Rautian Profile.
n4
n4
n4
n4
n4
n4
n4
n4
0.1123(28)
0.1147(37)
0.1113(30)
0.1107(27)
0.1086(28)
0.1101(26)
0.1054(38)
0.0748(19)
1.007±0.025
0.987±0.032
1.050±0.028
1.004±0.024
0.986±0.025
0.963±0.023
0.989±0.036
0.984±0.025
Mean & std. dev. 0.996±0.023
CONCLUSIONS
o Over 4000 line positions and intensities are measured.
o The rotational quantum numbers of measured lines go as high as J″=16
and K″=15 in the n1 and n3 bands.
o The measured positions and intensities are modeled using new
theoretical calculations in the pentad. The analyses are in progress.
o More than 800 Lorentz self-broadened widths and self-induced
pressure shift coefficients are measured in several bands.
o Off-diagonal relaxation matrix elements are determined for a number
of A+A- transitions with K″= 3, 6, and 9.
o Speed dependence parameters are also retrieved for several transitions.
ACKNOWLEDGMENTS
NASA’s Outer Planetary Research Program supported the work performed at the College of William and Mary. Research at
the Jet propulsion Laboratory (JPL), California Institute of Technology, was performed under contract with the National
Aeronautics and Space Administration. The United States Department of Energy supported part of this research and was
conducted at the W.R. Wiley Environmental Molecular Sciences laboratory, a national scientific user facility sponsored by
the Department of Energy’s Office of Biological and Environmental Research and located at the Pacific Northwest National
Laboratory (PNNL). PNNL is operated for the United States Department of Energy by the Battelle Memorial Institute under
Contract DE-AC05-76RLO 1830. I. Kleiner wishes to thank the financial support by ANR-08-BLAN-0054 for this project.
L.N. Fletcher acknowledges the support by a Glasstone Science Fellowship at the University of Oxford.
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