Transcript Methanol.ppt

The rotational-torsional
spectrum of methanol
Rogier Braakman, Caltech
John Pearson, JPL
Brian Drouin, JPL
Geoff Blake, Caltech
Motivation and Goals
•
Commissioning of Herschell and Sofia
–
Map uncharted THz regions between 480 GHz and 5 THz
–
Spectra of “known” molecules in ISM need to be
characterized; methanol one of the most abundant
Vt=0,1,2 all observed in ISM
–
•
Pure spectroscopic interest
–
Rotation-Torsion interaction: lines everywhere!
–
Extend assignments in Vt=0,1,2, include more DK
information
Assign Vt=3,4 and vibrational states where energy levels
are available
–
History
•
Previous global analyses including Vt=0,1 and 2
–
Limited in J and K
–
–
–
Neglected most TuFIR lines (eg. Matsushima et al.)
Ignored most Baskakov et al. GS lines
New data from Tsunekawa et al. not included
Refs: Belov et. al. 1995, Odashima et al. 1995, Xu & Lovas 1997
•
Energy levels up to J=45 and K=14 from Microwave, IR
& FIR spectra
–
Predictions not to microwave accuracy
Ref: Moruzzi et. al. 1995, Methanol Atlas
HIFI Spectrum:
• 452 – 485 GHz
• Room temp,
cold load
• Lots of U-lines
U-lines !!!
New data
• Almost continuously from 355-1200 GHz
plus regions around 1.6 and 1.8 THz
• Lines up to J~45, K~15-16 in GS
• States through Vt=4, VCO+Vt=1 and Vri
• Many, many new lines!
K=19-18 aR-branch region
Excited state transitions
Vt=4, K=0
Vt=4, K=4
VCOVt=1, K=0
Vri, K=3
VCO, K=5
Vt=2, K=4-3 Q branch
Analysis
• Eventually global fit describing all interactions
• Mean time: Check assignments, debug line files
• Power series fitting:
– Treat as rigid rotor
– K-stacks as vibrational states
– A and E states separately
• Vt=0, A state underway:
– 1500+ lines in fit, up to J=45, K=14
– K=9 problematic at high J
•
E state more problematic:
– K-stack crossings
A levels relative to K=0, vt=1
900
Energy (cm^-1)
700
500
300
100
0
5
10
15
20
-100
J
25
30
35
vt=1,K=1+
vt=1,K=1Vt=1.K=2+
vt=1,K=2vt=1,K=3+
vt=1,K=3vt=1,K=4
vt=1,K=5
vt=1.K=6
vt=1,K=7
vt=1,K=8
vt=1,K=9
vt=1,K=10
vt=1,K=11
vt=1,K=12
vt=1,K=14
vt=0,K=8
vt=0,k=9
vt=0,K=10
vt=0,K=11
vt=0,K=12
vt=0,K=13
vt=2,k=0+
vt=2,K=1+
vt=2,K=1vt=2,k=2+
vt=2,K=2vt=2,K=3
vt=2,K=4
vt=2,K=5
vt=2,K=6
vt=2,K=7
vt=2,K=8
vt=2,K=9
vt=2,K=10
vt=1,K=13
vt=0,K=14
vt=0,K=15
vt=2,k=11
vt=2,K=12
vt=2,K=13
vt=3,k=0+
vt=3,k=1vt=3,K=1+
vt=3,K=2+
vt=3,k=2vt=3,k=3+
vt=3,k=3vt=3,k=4
vt=3,k=5
vt=3,k=6
A levels relative to K=0, vt=1
0
0
5
10
15
20
-1
-1
Energy (cm^-1)
-2
-2
-3
-3
vt=1,K=5
-4
-4
vt=0,k=9
-5
-5
J
25
30
35
A levels relative to K=0, vt=1
-68
0
5
10
15
20
-69
-69
Energy (cm^-1)
-70
-70
-71
vt=1,K=1+
-71
vt=1,K=1-72
vt=0,K=8
-72
J
25
30
35
Summary
• Extensive new spectral database
• Assignments in ground and many excited states
(Vt=0,1,2,3,4, VCO+Vt=0,1, Vri)
– Locating b-types
– Mapping level crossings
• Fitting of ground state underway, to be followed
by Vt=1,2,3,….
Thanks
Group members:
•
•
•
•
Dan Holland
Vadym Kapinus
Matthew Kelley
Susanna Widicus Weaver
HIFI spectrum:
• David Teyssier
• Claudia Comito
Funding:
• NASA
• NSF