rotational spectroscopy of co solvated with para-h 2 molecules paul raston and wolfgang jäger...
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![Page 1: ROTATIONAL SPECTROSCOPY OF CO SOLVATED WITH PARA-H 2 MOLECULES Paul Raston and Wolfgang Jäger Department of Chemistry, University of Alberta, Edmonton,](https://reader035.vdocument.in/reader035/viewer/2022062804/5697bf741a28abf838c7fbc8/html5/thumbnails/1.jpg)
ROTATIONAL SPECTROSCOPY OF CO SOLVATED ROTATIONAL SPECTROSCOPY OF CO SOLVATED WITH WITH PARAPARA-H-H22 MOLECULES MOLECULES
Paul Raston and Wolfgang JägerDepartment of Chemistry, University of Alberta, Edmonton, AB Canada
OSU 2009
S. Baroni and S. Moroni, ChemPhysChem 6, 1884 (2005)
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parapara-H-H22 clusters clusters
*P. Sindzingre, D. M. Ceperley, M. L. Klein, Phys. Rev. Lett. 67, 1871 (1991)
Low temperature (<2 K) para-H2 clusters are liquid like
Small pH2 clusters predicted to be superfluid below ~2 K.*
Rotational temperature of seeded clusters <1 K
In this study NpH2<8
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Sample & conditionsSample & conditions
Typically used 0.05-1% CO + 1-10% pH2 in Helium up to 150 bar
Nozzle cooled down to -40°C
Normal H2 (75% ortho- + 25% para-) converted to >97% pH2 in catalytic converter held at <20K for several hours
I. F. Silvera, Rev. Mod. Phys. 52, 393 (1980)
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FTMWFTMW spectrometerspectrometer
Pulsed molecular beam polarized with MW’s: Coherent emission is recorded
Good up to ~27 GHz, below which 6 (pH2)N-CO end-over-end transitions should lie
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paraparaHH22-CO dimer-CO dimer
A.V. Potapov, L.A. Surin, V.A. Panfilov, B.S. Dumesh, T.F. Giesen, S. Schlemmer, P.L. Raston and W. Jäger, in preparation.
We know 101-000 transition frequency for N=1 to within ±50 kHz
0
5
10
15
20
25
C O H para 2
J j l, , C O
00 010 1
20 2
30 3
50 5
60 6
40 4
11 0211
31 2
41 3
51 4
61 5
111
21 2
31 3
41 4
51 5
011
11 2
21 3
31 4
41 5
6 61
K e=0( )
K e=1( )
K= (f)1
K e=0( ), =1b ,C O
c
a
b
O
C
H 2
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N0 1 2 3 4 5 6 7 8 9
Fre
quen
cy /
MH
z
0
10000
20000
30000
40000
50000
TheoryIRMW
ppHH22-CO-CO
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Previous IR studyPrevious IR study
S. Moroni, M. Botti, S. De Palo, A. R. W. McKellar, J. Chem. Phys. 122, 094314 (2005)
R1(0) line observed for NpH2<18
Not able to fully separate rotational and vibrational contributions to line position
N
0 1 2 3 4 5 6 7 8 9
Wav
enum
ber
/ cm
-1
2142.4
2142.6
2142.8
2143.0
2143.2
2143.4
2143.6
2143.8
2144.0
2144.2
2144.4
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N0 1 2 3 4 5 6 7 8 9
Fre
quen
cy /
MH
z
0
10000
20000
30000
40000
50000
TheoryIRMW
MW predictions from:MW predictions from:
Assumption that the vibrational shift scales linearly with N
S. Moroni, M. Botti, S. De Palo, A. R. W. McKellar, J. Chem. Phys. 122, 094314 (2005)
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MW predictions from:MW predictions from:
Assumption that the vibrational shift scales linearly with N
Reptation Monte Carlo simulations
S. Moroni, M. Botti, S. De Palo, A. R. W. McKellar, J. Chem. Phys. 122, 094314 (2005)
N0 1 2 3 4 5 6 7 8 9
Fre
quen
cy /
MH
z
0
10000
20000
30000
40000
50000
TheoryIRMWCol 1 vs Col 6
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N0 1 2 3 4 5 6 7 8 9
Fre
quen
cy /
MH
z
0
10000
20000
30000
40000
50000
TheoryIRMWCol 1 vs Col 6
MW linesMW lines
N=2 found close to IR predicted value
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N0 1 2 3 4 5 6 7 8 9
Fre
quen
cy /
MH
z
0
10000
20000
30000
40000
50000
TheoryIRMW
MW linesMW lines
N=3-6 increasingly further from IR predicted values
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N0 1 2 3 4 5 6 7 8 9
Fre
quen
cy /
MH
z
0
10000
20000
30000
40000
50000
TheoryIRMWCol 1 vs Col 6
MW linesMW lines
Turnaround of rotational frequency in going from N=6 to 7
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N
Wav
enum
ber
/ cm
-1
2141.8
2142.0
2142.2
2142.4
2142.6
2142.8
2143.0
2143.2
2143.4
ActualAssumed (linear shift with N)
N
0 1 2 3 4 5 6 7 8
Fre
quen
cy /
MH
z
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
Difference
Vibrational shiftVibrational shift
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N
Wav
enum
ber
/ cm
-1
2141.8
2142.0
2142.2
2142.4
2142.6
2142.8
2143.0
2143.2
2143.4
ActualAssumed (linear shift with N)
N
0 1 2 3 4 5 6 7 8
Fre
quen
cy /
MH
z
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
Difference
Vibrational shiftVibrational shift
Switched IR assignment for N=6 & 7
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N0 1 2 3 4 5 6 7 8 9
Fre
quen
cy /
MH
z
12000
14000
16000
18000
20000
22000
24000
12161316
((ppHH22))NN--1313CC1616O MW linesO MW lines
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((ppHH22))NN--1313CO MW linesCO MW lines
N0 1 2 3 4 5 6 7 8 9
Fre
quen
cy /
MH
z
12000
14000
16000
18000
20000
22000
24000
12161316
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((ppHH22))NN--1313CO MW linesCO MW lines
Number of pH2 molecules
1 2 3 4 5 6 7 8
1216
/131
6
1.00
1.01
1.02
1.03
1.04
1.05"free" CO
solid pH2
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SummarySummary
1216 1316 Assignment
22200.54 22054.30 (pH2)2-CO
16455.81 16326.93 (pH2)3-CO
15107.44 14959.44 (pH2)4-CO
14633.25 14473.32 (pH2)5-CO
13243.82 13096.04 (pH2)6-CO
17723.12 17403.17 (pH2)7-CO
15834.58 15727.36 pH2-He-CO
*Tentative
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OutlookOutlook
MW transitions of (pH2)N=2-7-CO (1216 and 1316) measured and assigned
Turnaround in rotational frequency observed in going from N=6 to 7
Extend frequency range of spectrometer and search for N=8 at 30-40+ GHz….
Find 1218 and 1318 lines
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AcknowledgementsAcknowledgements
Jäger group
Xu group
A.R.W. McKellar
Funding: University of Alberta Natural Science and Engineering Research Council of Canada Canada Foundation for Innovation Alberta Science and Research Investments Program
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PESPES
• Reptation Monte Carlo algorithm used to simulate rotational dynamics for NpH2<18
• N=incremental density distribution
C O
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AssignmentAssignment
Ratio of line intensities for 2 different gas mixtures differing only in the [pH2]; The 2nd mixture contained 0.125x the [pH2] in the 1st
N
1 2 3 4 5 6 7 8
Inte
nsit
y ra
tio
e0
e1
e2
e3
e4
e5
e6
e7
Assignments mostly from concentration dependence of line intensities
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Comparison with HD solvated HCNComparison with HD solvated HCN
D. T. Moore, R. E. Miller, J. Chem. Phys. 119, 4713 (2003)
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/ MHz
17722.8 17723.0 17723.2 17723.4 17723.6