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Continuous-wave Cavity Ringdown Study of the First Positive Band System of N 2 *. Brett A. McGuire Susanna L. Widicus Weaver † Michael Wiczer Bogdan Negru ‡ Joshua P. DiGangi * Brian A. Tom Benjamin J. McCall. Departments of Chemistry and Astronomy, - PowerPoint PPT Presentation
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June 18, 2008June 18, 2008 The University of IllinoisThe University of Illinois 1
Continuous-wave Cavity Ringdown Study of the First Continuous-wave Cavity Ringdown Study of the First Positive Band System of NPositive Band System of N22
**
Brett A. McGuireBrett A. McGuireSusanna L. Widicus WeaverSusanna L. Widicus Weaver††
Michael WiczerMichael WiczerBogdan NegruBogdan Negru‡
Joshua P. DiGangi*Joshua P. DiGangi*Brian A. TomBrian A. Tom
Benjamin J. McCallBenjamin J. McCall
Departments of Chemistry and Astronomy,
University of Illinois at Urbana-Champaign†Department of Chemistry, Emory University
‡Department of Chemistry, University of California, Berkeley
*Department of Chemistry, University of Wisconsin-Madison
June 18, 2008June 18, 2008 The University of IllinoisThe University of Illinois 22
OutlineOutline Motivations
Practical Scientific
BackgroundBackground Experimental DetailsExperimental Details Previous WorkPrevious Work
Spectral CalibrationSpectral Calibration Mode HopsMode Hops Frequency DeterminationFrequency Determination
AssignmentsAssignments DifficultiesDifficulties Progress and Molecular ConstantsProgress and Molecular Constants
Conclusions and Future WorkConclusions and Future Work
June 18, 2008June 18, 2008 The University of IllinoisThe University of Illinois 33
MotivationsMotivations
PracticalPractical Stepping Stone for Ringdown ExperimentsStepping Stone for Ringdown Experiments
Software SuiteSoftware Suite Hardware and opticsHardware and optics Fundamental TechniquesFundamental Techniques
Demonstrates Need for Ion/Neutral DiscriminationDemonstrates Need for Ion/Neutral Discrimination Motivation for SCRIBESMotivation for SCRIBES
ScientificScientific Unobserved/unassigned bandsUnobserved/unassigned bands
BecauseIt’s
There!
WG10 – Andrew Mills
June 18, 2008June 18, 2008 The University of IllinoisThe University of Illinois 44
OutlineOutline MotivationsMotivations
PracticalPractical ScientificScientific
Background Experimental Details Previous Work
Spectral CalibrationSpectral Calibration Mode HopsMode Hops Frequency DeterminationFrequency Determination
AssignmentsAssignments DifficultiesDifficulties Progress and Molecular ConstantsProgress and Molecular Constants
Conclusions and Future WorkConclusions and Future Work
June 18, 2008June 18, 2008 The University of IllinoisThe University of Illinois 55
Experimental SetupExperimental Setup
Ar/N2 Discharge
3100 V, 70mA
June 18, 2008June 18, 2008 The University of IllinoisThe University of Illinois 66
CW Cavity Ringdown Spectroscopy (cw-CRDS)CW Cavity Ringdown Spectroscopy (cw-CRDS)
Laser AOM
R ≥ 99.99%
June 18, 2008June 18, 2008 The University of IllinoisThe University of Illinois 77
Needles in the HaystackNeedles in the Haystack
June 18, 2008June 18, 2008 The University of IllinoisThe University of Illinois 88
The First Positive Group (BThe First Positive Group (B33ΠΠgg – A – A33ΣΣgg++) of N) of N22
n''n'
0 1 2 3 4 5 6 7 8 9
0 9512 8079 6674 5297 3947 2625 1332
1 11217 9784 8379 7002 5652 4331 3037 1772 535
2 12894 11461 10056 8678 7329 6007 4713 3448 2212 1004
3 14540 13108 11703 10326 8976 7654 6361 5096 3859 2681
4 16160 14727 13321 11944 10594 9273 7979 6714 5477 4270
5 17749 16316 14911 13513 12184 10862 9668 8303 7067 5859
6 19309 17876 16471 16093 14742 12422 11129 9862 8627 7419
7 20840 19407 18002 16625 16274 13963 12660 11395 10158 8960
8 20909 19504 18126 16777 16455 14161 12896 11670 10462
9 20976 19599 18249 26927 16612 14369 13132 11924
10 21041 19692 18310 17076 16811 14575 13307
11 21105 19873 18489 17224 15988 14780
12 21166 19873 18607 17370 16163
First observed in the First observed in the visible by Deslandres in visible by Deslandres in
19021902(C. R. Society, Paris, 134)(C. R. Society, Paris, 134)
CalculatedExperimental
Adapted from Dieke & Heath Johns Hopkins Spec. Report 17, 1959& Roux & Michaud J. Mol. Spec. 97, 253, 1983.
10200 – 10600 cm-1 diode laser
June 18, 2008June 18, 2008 The University of IllinoisThe University of Illinois 99
OutlineOutline MotivationsMotivations
PracticalPractical ScientificScientific
BackgroundBackground Experimental DetailsExperimental Details Previous Work Previous Work
Spectral Calibration Mode Hops Frequency Determination
AssignmentsAssignments DifficultiesDifficulties Progress and Molecular ConstantsProgress and Molecular Constants
Conclusions and Future WorkConclusions and Future Work
June 18, 2008June 18, 2008 The University of IllinoisThe University of Illinois 1010
Spectral CalibrationSpectral Calibration
June 18, 2008June 18, 2008 The University of IllinoisThe University of Illinois 1111
Spectral CalibrationSpectral Calibration
June 18, 2008June 18, 2008 The University of IllinoisThe University of Illinois 1212
Spectral CalibrationSpectral Calibration9
June 18, 2008June 18, 2008 The University of IllinoisThe University of Illinois 1313
Spectral CalibrationSpectral Calibration
June 18, 2008June 18, 2008 The University of IllinoisThe University of Illinois 1414
Spectral CalibrationSpectral Calibration
June 18, 2008June 18, 2008 The University of IllinoisThe University of Illinois 1515
Concatenated SpectraConcatenated Spectra
0.03 cm-1
αmin = 5 x 10-10 cm-1
June 18, 2008June 18, 2008 The University of IllinoisThe University of Illinois 1616
OutlineOutline MotivationsMotivations
PracticalPractical ScientificScientific
BackgroundBackground Experimental DetailsExperimental Details Previous Work Previous Work
Spectral CalibrationSpectral Calibration Mode HopsMode Hops Frequency DeterminationFrequency Determination
Assignments Difficulties Progress and Molecular Constants
Conclusions and Future Work
Today’sToday’sAssignmentAssignment
June 18, 2008June 18, 2008 The University of IllinoisThe University of Illinois 1717
Pressure DifferentiationPressure Differentiation
N2*
N2+
June 18, 2008June 18, 2008 The University of IllinoisThe University of Illinois 1818
Spectral ParametersSpectral Parameters
119 Lines assigned with an RMS of 0.01 cm-1
PGOPHER, a Program for Simulating Rotational Structure, C. M. Western,
University of Bristol, http://pgopher.chm.bris.ac.uk
ParameteParameterr
Our ValuesOur Values
Ground StateGround State
B 1.391092(79)1.391092(79)
λ -1.3152(23)-1.3152(23)
γ x 104 -6.97(92)-6.97(92)
D x 106 6.303(98)6.303(98)
Upper StateUpper State
Origin 10364.126810364.1268
B 1.575317(79)1.575317(79)
A 43.1339(18)43.1339(18)
λ -0.6552(52)-0.6552(52)
o -1.0018(30)-1.0018(30)
p x 102 1.370(26)1.370(26)
q x 104 -1.31(11)-1.31(11)
D x 106 6.705(96)6.705(96)
June 18, 2008June 18, 2008 The University of IllinoisThe University of Illinois 1919
A Lot Left To Go…A Lot Left To Go…
June 18, 2008June 18, 2008 The University of IllinoisThe University of Illinois 2020
Conclusions and Future WorkConclusions and Future Work
The cw-CRDS spectra of N2+ and N2* from 10227 – 10590 cm-1 have been
acquired
125 N2+ lines from the 2-1 band of the Meinel system have been assigned
and spectral parameters determined.‡
119 N2* lines from the 3-3 band have been assigned and spectral parameters determined.
Many of the weaker lines are most likely assignable Nail down the fit, finalize the constants Compare to those from the global fit of Roux et al.†
Lines from the 2-2, 4-4, 7-8, and 8-9 bands may also be visible in this region and will be analyzed in future studies.
‡Widicus Weaver et al., J. Mol. Spec., 249, 2008†Roux et al., J. Mol. Spec. 97, 1983
June 18, 2008June 18, 2008 The University of IllinoisThe University of Illinois 2121
AcknowledgementsAcknowledgements
Susanna Widicus Weaver and Ben McCall
Former group members Joshua DiGangi, Bogdan
Negru, and Michael Wiczer
Dr. Colin Western at the University of Bristol for the fitting program PGOPHER
NSF CHEACS
DreyfusUIUC
NASA LaboratoryAstrophysics
Brian Tom
Ben McCall
The McCall Group
http://bjm.scs.uiuc.edu/