Transcript NO-alkane-edit.pptx

Electronic Spectroscopy of the NO-X (X = Rare
Gas, Alkane) Complexes.
Adrian Gardner, Victor Tamé-Reyes, Joe Harris,
Jodie McDaniel and Timothy Wright
67th International Symposium on Molecular Spectroscopy
Ohio State University
21st June 2012
Introduction
• Nitric oxide is a radical with a degenerate ground electronic state of 2Π.
• It has a series of relatively low-lying Rydberg states which converge to the 1Σ+ cationic state.
• The lowest energy of these corresponds to a 3s ← 2pπ* transition, with the dipole of the
excited state of 1.1 Debye being significantly larger than the 0.1 Debye of the ground state.
X̃ D0 / cm-1
à D0 / cm-1
NO–Ne1
28.6
--
NO–Ar1
93.8
50.6
NO–Kr2
105.4
103.7
NO–Xe2
121.3
157.6
• The aim of the present study is to investigate the à state complexes of NO with a related
series of molecules.
1. H. L. Holmes-Ross and W. D. Lawrance, J. Chem. Phys., 135, 014302 (2011)
2. Gamblin et al., Chem. Phys. Lett., 325, 232, (2000).
Experimental Apparatus
NO-alkane à ← X̃ Spectra
NO–methane3
NO–ethane4
NO–propane
NO–butane
Wavenumber relative to à state origin / cm-1
3. Musgrave et al., J. Chem. Phys., 123, 204305 (2005).
4. Daire et al., J. Phys. Chem. A, 104, 9180 (2000).
NO-alkane à ← X̃ Spectra
D0″ may be determined using the relationship:
T0[NO–alkane] - NO[Q11(0.5)] = D0″ - D0′
X̃ D0 / cm-1
à D0 / cm-1
NO–methane3
106.4
201.5
NO–ethane4
180
330
NO–propane
245
430
NO–butane
310
480
3. Musgrave et al., J. Chem. Phys., 123, 204305 (2005).
4. Daire et al., J. Phys. Chem. A, 104, 9180 (2000).
NO-(propane)2 Ã ← X̃ Spectra
NO + Pr + Pr
Recorded in NO–propane
mass channel
NO + Pr + Pr
Recorded in NO–(propane)2 mass
channel
• A value for D0 of ~880 cm-1 is determined for the NO–(propane)2 complex in the à state,
relative to the NO(A) + propane + propane asymptote.
• This value is approximately twice that determined for the NO–propane complex.
NO-(propane)2 Spectra
NO-(propane)2 Spectra
≥
≤
• The De of the propane dimer has been calculated to be 728 cm-1 at the MP2/complete basis
set limit using aVTZ and aVQZ basis sets.7
7. Tsuzuki et al., J. Chem. Phys.,124, 114304 (2006).
NO-(butane)n Spectra
NO + Bu + Bu
• No signal could be observed in the NO–(butane)2 mass channel.
• The high energy limit observed in the NO–butane mass channel may initially be
rationalized as accessing the NO + butane + butane dissociation continuum.
NO-(butane)n Spectra
480 cm-1
44198.9 cm-1
≥45040 cm-1
44030 cm-1
310 cm-1
≥560 cm-1
NO-(ethane)2 Spectrum
•
Shown above is the Ã←X̃ spectrum recorded in the NO–(ethane)2 mass channel, reported in Ref. 4.
•
The dissociation energy of the à state of the NO–(ethane)2 complex, relative to the NO + ethane +
ethane asymptote, has been determined to be ~350 cm-1, compared to 340 cm-1 of NO–ethane.4
•
Using a thermodynamic cycle, the D0″ of NO–(ethane)2 is determined to be ~260 cm-1, which is
higher than that of NO–(ethane), but considerably lower than that calculated for the ethane dimer
of 473 cm-1.5
4. Daire et al., J. Phys. Chem. A, 104, 9180 (2000). 5.Tsuzuki et al., J. Chem. Phys.,124, 114304 (2006).
NO-(ethane)n Spectra
NO + Et + Et
Recorded in the NO–ethane
mass channel
Recorded in the NO–(ethane)2
mass channel
Recorded in the NO–(ethane)3
mass channel
43600
43800
44000
44200
44400
44600
44800
Wavenumber /
cm-1
45000
45200
45400
45600
45800
NO-(ethane)n Spectra
NO-(ethane)n Spectra
NO-(ethane)n Spectra
NO + Et + Et
Recorded in the NO–ethane
mass channel
NO–Et + Et + Et
Recorded in the NO–(ethane)2
mass channel
NO–Et+ Et + Et
Recorded in the NO–(ethane)3
mass channel
43600
43800
44000
44200
44400
44600
44800
Wavenumber /
cm-1
45000
45200
45400
45600
45800
NO-(ethane)n Spectra
NO-(ethane)n Spectra
Conclusions
• (1 + 1) REMPI spectra corresponding to the à ← X̃ transition for NO–propane and
NO–butane have been recorded.
• Dissociation energies for both the ground and excited states have been determined, with
the à state always more strongly bound than the X̃ state.
• Comparison with values previously determined for the NO–methane and NO–ethane
complexes show an expected increase in D0 with increasing alkane chain length.
• Dissociation energies determined for the X̃ state of the NO–(ethane)2, NO–(propane)2
and NO–(butane)2 complexes suggests that their structures are of the form: NO–alkane–
alkane.
Acknowledgements
Professor Timothy Wright
Victor Tamé-Reyes
Joe Harris
Jodie McDaniel