1 62nd ohio state university international symposium on molecular spectroscopy, talk tj06, 19 june...
TRANSCRIPT
162nd Ohio State University International Symposium on Molecular Spectroscopy, Talk TJ06, 19 June 2007, Columbus, OH.
Approved for Public Release; Distribution Unlimited. AAC/PA 06-07-07-440.
Mario E. Fajardo, C. Michael LindsayAFRL/MNME, Energetic Materials Branch, Ordnance Division,
U.S. Air Force Research Laboratory, 2306 Perimeter Road, Eglin AFB, FL 32542-5910. [email protected]
&
David T. AndersonDepartment of Chemistry, University of Wyoming, Laramie, WY 82071-3838.
* Gas phase (HCl)2 – “geared” internal rotation/tunneling.
* “Broken-symmetry allowed” transitions in H35Cl-H37Cl.
* High-res IR spectra of (HCl)2 isotopomers in solid pH2.
* “Tunneling” splittings in H35Cl-H37Cl/pH2 (± 0.002 cm-1).
* CAVEAT! spectroscopic assignments incomplete, so conclusions in re tunneling still "tentative."
HCl Dimer in Solid Parahydrogen Revisited
262nd Ohio State University International Symposium on Molecular Spectroscopy, Talk TJ06, 19 June 2007, Columbus, OH.
Approved for Public Release; Distribution Unlimited. AAC/PA 06-07-07-440.
Gas Phase (HCl)2
donor (2)
acceptor (1)
(HCl)2:
nearly prolate symmetric top( -1.0)
donor (2) mode||, a-type, Ka=0,
acceptor (1), b-type, Ka=±1
tunneling interconversion of HCl subunits; "geared" bending;R‡
HCl-HCl < 0.004Å
362nd Ohio State University International Symposium on Molecular Spectroscopy, Talk TJ06, 19 June 2007, Columbus, OH.
Approved for Public Release; Distribution Unlimited. AAC/PA 06-07-07-440.
Broken-Symmetry Transitions
M.D. Schuder, C.M. Lovejoy, R. Lascola, and D.J. Nesbitt, J. Chem. Phys. 99, 4346 (1993).
+
+
2+ 2
15.5 cm-1
3.2 cm-1
H35Cl-H35Cl & H37Cl-H37Clrigorous inversion symmetry
+ - selection rules
+
+
2+ 2
H35Cl-H37Cl & H37Cl-H35Clno inversion symmetry
new IR transitions; 12x weaker
462nd Ohio State University International Symposium on Molecular Spectroscopy, Talk TJ06, 19 June 2007, Columbus, OH.
Approved for Public Release; Distribution Unlimited. AAC/PA 06-07-07-440.
Low-lying (HCl)2 States
M.D. Schuder, C.M. Lovejoy, R. Lascola, and D.J. Nesbitt, J. Chem. Phys. 99, 4346 (1993).
Ka0 1
gas-
phas
e ro
vibr
atio
nal o
rigin
s (c
m-1
)
0
10
202850
2860
2870
2880
2890
2900
--35-35--
--35-35--
--35-35--
--35-35--
--35-35--
--35-35--
--35-35--
--35-35--
--35-35--
--35-35--
--35-35--
--35-37--
--35-37--
--35-37--
--35-37--
--35-37--
--35-37--
--35-37--
--35-37--
--35-37--
--35-37--
--35-37--
--37-37--
--37-37--
--37-37--
--37-37--
--37-37--
--37-37--
--37-37--
--37-37--
--37-37--
--37-37--
=0 =1
=0 =1
562nd Ohio State University International Symposium on Molecular Spectroscopy, Talk TJ06, 19 June 2007, Columbus, OH.
Approved for Public Release; Distribution Unlimited. AAC/PA 06-07-07-440.
HCl & (HCl)2 in solid pH2
3.8 Å
gas phase HCl dimer dimer is nearly perfect fit!
pH2 nearest neighbor spacing
BpH2(HCl) 0.93 Bgas(HCl) monomer is nearly free rotor*
3.8 Å
Can A-axis rotation & internal dynamics survive immersion in solid pH2 environment?
* D.T. Anderson, R.J. Hinde, S. Tam and M.E. Fajardo, J. Chem. Phys. 116, 594 (2002).
662nd Ohio State University International Symposium on Molecular Spectroscopy, Talk TJ06, 19 June 2007, Columbus, OH.
Approved for Public Release; Distribution Unlimited. AAC/PA 06-07-07-440.
Rapid vapor deposition of solid pH2
M.E. Fajardo and S. Tam, J. Chem. Phys. 108, 4237 (1998).S. Tam and M.E. Fajardo, Rev. Sci. Instrum. 70, 1926 (1999).S. Tam and M.E. Fajardo, J. Low Temp. Phys. 122, 345 (2001).
Deposition conditions: Tconv = 15 K
100 ppm oH2
Tconv = 19 K
1000 ppm oH2
npH2/t = 200 mmol/hr
x/t = 3.1 mm/hr Tsub = 2.4 K 2.9 K
TpH2 4.6 K
Result: mixed fcc/hcp microstructure in as-deposited samples;can anneal to pure hcp.
762nd Ohio State University International Symposium on Molecular Spectroscopy, Talk TJ06, 19 June 2007, Columbus, OH.
Approved for Public Release; Distribution Unlimited. AAC/PA 06-07-07-440.
Low Temperature Stick Spectrum
M.D. Schuder, C.M. Lovejoy, R. Lascola, and D.J. Nesbitt, J. Chem. Phys. 99, 4346 (1993).
wavenumber (cm-1)
2820 2830 2840 2850 2860 2870 2880 2890 2900 2910 2920
sim
ulat
ed a
bsor
banc
e (a
rb.)
35-3535-3737-3735-37 B.S.monomer
monomerR(0)
BS
BS
862nd Ohio State University International Symposium on Molecular Spectroscopy, Talk TJ06, 19 June 2007, Columbus, OH.
Approved for Public Release; Distribution Unlimited. AAC/PA 06-07-07-440.
wavenumber (cm-1)
2725 2750 2775 2800 2825 2850 2875 2900 2925
log
10(I
0/I)
(ab
s.)
0.0
0.5
1.0
1.5
monomerR(0)
dimer
dimer
trimer(HCl)3
tetramer(HCl)4
88 ppm HCl/pH2 (annealed)
HCl/pH2
0=2876 cm-1
number of HCl molecules
0 1 2 3 4 5
vibr
atio
nal s
hift
(cm
-1)
-150
-100
-50
0
50
gas phase*pH2
* M. Farnik, S. Davis, and D.J. Nesbitt, Faraday Disc. 118, 63 (2001).
*
962nd Ohio State University International Symposium on Molecular Spectroscopy, Talk TJ06, 19 June 2007, Columbus, OH.
Approved for Public Release; Distribution Unlimited. AAC/PA 06-07-07-440.
(HCl)2/pH2
wavenumber (cm-1)
2800 2810 2820 2830 2840 2850 2860 2870 2880 2890 2900
log
10(I
0/I)
(ab
s.)
0.0
0.5
1.0
1.5
monomerR(0)
BS
1062nd Ohio State University International Symposium on Molecular Spectroscopy, Talk TJ06, 19 June 2007, Columbus, OH.
Approved for Public Release; Distribution Unlimited. AAC/PA 06-07-07-440.
2+ region (HCl)2/pH2
wavenumber (cm-1)
2832 2833 2834 2835 2836 2837
log
10(I
0/I)
(ab
s.)
0
1
23535
3535
3537/
3537
3537
3537 37
37
3737
a
b
c
brokensymmetry
2+ ?!
naturalabundance
37Cl enriched
35Cl enriched
1162nd Ohio State University International Symposium on Molecular Spectroscopy, Talk TJ06, 19 June 2007, Columbus, OH.
Approved for Public Release; Distribution Unlimited. AAC/PA 06-07-07-440.
Eglin AFB Experimental Setup
s
p
HCP c-axis ??
p-H2
gold substrate
s
p
HCP c-axis ??
p-H2
gold substrate
1262nd Ohio State University International Symposium on Molecular Spectroscopy, Talk TJ06, 19 June 2007, Columbus, OH.
Approved for Public Release; Distribution Unlimited. AAC/PA 06-07-07-440.
Polarization Dependence
wavenumber (cm-1)
2832 2833 2834 2835 2836 2837
log
10(I
0/I)
(ab
s.)
-0.2
-0.1
0.0
0.1
0.2
0.3
0.4
0.5
0.6
3537
3537
3537
3537
3535
3535
3737
3737
(a)
(b)
* oH2 - HCl complex in-plane (HCl)2
|| out-of-plane (HCl)2
1362nd Ohio State University International Symposium on Molecular Spectroscopy, Talk TJ06, 19 June 2007, Columbus, OH.
Approved for Public Release; Distribution Unlimited. AAC/PA 06-07-07-440.
H35Cl-H37Cl Tunneling Splittings (?)
2+ K=00 gas phase solid pH2 gas - pH2 ip - oop
H35Cl-H35Cl 2857.235 2835.701 21.534 0.630
2836.331 || 20.904
H35Cl-H37Cl 2856.449 2835.153 21.296 0.594
2835.747 || 20.702
H37Cl-H37Cl 2855.106 2833.557 21.549 0.638
2834.195 || 20.911
H35Cl-H37Cl 2852.717 2832.902 19.815 0.511broken symmetry 2833.413 || 19.304
v2=1 H35Cl-H37Cl: Egas = 3.7320(4) cm-1, Eip = 2.250(1) cm-1, Eoop = 2.335(1) cm-1
1462nd Ohio State University International Symposium on Molecular Spectroscopy, Talk TJ06, 19 June 2007, Columbus, OH.
Approved for Public Release; Distribution Unlimited. AAC/PA 06-07-07-440.
1+ region (HCl)2/pH2
wavenumber (cm-1)
2860 2865 2870 2875 2880
log
10(I
0/I)
(ab
s.)
0.00
0.05
0.10
0.15
0.20
0.25
3537
3535
3737
(a)
(c)
(b)
oH2 -
H35
Cl
oH2 -
H35
Cl
oH2 -
H37
Cl
oH2 -
H37
Cl
naturalabundance
37Cl enriched
35Cl enriched
brokensymmetry
1+ ?!
1562nd Ohio State University International Symposium on Molecular Spectroscopy, Talk TJ06, 19 June 2007, Columbus, OH.
Approved for Public Release; Distribution Unlimited. AAC/PA 06-07-07-440.
Unassigned Hot Bands
wavenumber (cm-1)
2800 2810 2820 2830 2840 2850 2860 2870 2880 2890 2900
log
10(I
0/I)
(ab
s.)
0.0
0.1
0.2
0.3
T = 4.8 K
T = 2.4 K
1662nd Ohio State University International Symposium on Molecular Spectroscopy, Talk TJ06, 19 June 2007, Columbus, OH.
Approved for Public Release; Distribution Unlimited. AAC/PA 06-07-07-440.
Summary
* Observed several rovibrational transitions of (HCl)2 isotopologes in solid pH2; assignments incomplete.
* New polarization measurements show that ubiquitous 0.5 cm-1 splitting in 2
+ region arises from in-plane (ip) and out-of-plane (oop) HCl dimers in hcp solid.
* Assignment of 2+ region consistent with observation of
broken symmetry transition of mixed H35Cl-H37Cl dimer.
* Assignment implies tunneling splittings for v2=1 of H35Cl-H37Cl: Eip = 2.250(1) cm-1, Eoop = 2.335(1) cm-1.
* Assignment of weak hot-bands underway.