Time-of-flight spectroscopy of high-overtone mode-selective vibrational excitation of CF/sub 4/ and SF/sub 6/ in collisions with H/sup +/(D/sup +/) at energies between 10 and 28 eV
Time-of-flight spectra for H/sup +/(D/sup +/)--CF/sub 4/ and SF/sub 6/ collisions have been measured with an improved resolution and at higher collision energies (10< or =E/sub lab/ < or =28 eV) compared to earlier work. In the low energy region (< or =13 eV) new distinct peaks are resolved for both molecules corresponding to small contributions from the second infrared active ..nu../sub 4/ mode in addition to the dominant ..nu../sub 3/ mode observed previously. Reexamination of experimental vibrational transition probabilities reveals an almost perfect agreement with a Poisson distribution for both modes up to the n = 6 overtone transition of ..nu../sub 3/. A simple straight line theory is used to calculate the energy transfer in small angle scattering from the long-range potential in good agreement with a full classical trajectory calculation. With this theory dipole moment derivatives can be determined directly from the observed energy transfers and are found to agree well with previous infrared measurements. At larger collision energies (> or =16 eV) an additional low intensity vibrational distribution is identified in the high energy loss tail of the spectra which can be attributed to small impact parameter collisions which probe the repulsive region of the potential. The observed energy transfers are also in good agreement with trajectory calculations indicating that the forced oscillator model is also applicable in the repulsive potential region for the present systems. A closer examination of the high energy loss tail reveals resolved structure which has been assigned to discrete states of the ..nu../sub 3/ mode in CF/sub 4/ up to the n = 14 overtone. These new results demonstrate that H/sup +/(D/sup +/) energy loss scattering can provide spectroscopic information not readily available from other experiments.
- Research Organization:
- Max Planck Institut fuer Stroemungsforschung, Boettingerstr. 4-8, 3400 Goettingen, Federal Republic of Germany
- OSTI ID:
- 5622320
- Journal Information:
- J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 83:5; ISSN JCPSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
ATOMIC IONS
CARBON TETRAFLUORIDE
CATIONS
CHARGED PARTICLES
COLLISIONS
ENERGY LEVELS
ENERGY RANGE
ENERGY-LEVEL TRANSITIONS
EV RANGE
EV RANGE 10-100
EXCITATION
EXCITED STATES
FLUORIDES
FLUORINATED ALIPHATIC HYDROCARBONS
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
HALOGENATED ALIPHATIC HYDROCARBONS
HYDROGEN IONS
HYDROGEN IONS 1 PLUS
ION COLLISIONS
ION-MOLECULE COLLISIONS
IONS
MOLECULE COLLISIONS
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
SULFUR COMPOUNDS
SULFUR FLUORIDES
VIBRATIONAL STATES