Infrared multiphoton excitation of small polyatomic molecules

Thesis/Dissertation · Sat Jan 01 04:00:00 EST 1983

OSTI ID:5471092

Simpson, T B

A systematic study of the collisionless infrared multiphoton excitation (IRMPE) and dissociation (IRMPD) of three and four atom molecules is presented. Specifically, collisionless IRMPE and IRMPD of a molecule with only three vibrational modes, SO/sub 2/, is shown for the first time. Experiments on OCS show that, like other small molecules, very high laser intensity is necessary for IRMPE. This is at variance with previously published results. A four atom molecule, NH/sub 3/, can undergo IRMPD, but shows the effects of the large anharmonicity of the pumped vibrational transition. Another four atom molecule, DN/sub 3/, undergoes interesting chemistry following IRMPD. The dissociation fraction for each of the small molecules is only on the order of 10/sup -3/ at laser intensities of 100 GW/cm/sup 2/ and fluences of 100 J/cm/sup 2/. Though NO/sub 2/ at low vibrational energy does not undergo IRMPE under CO/sub 2/ laser excitation, it will undergo IRMPE if previously excited to high vibrational levels by a visible laser. Near the dissociation threshold strictly fluence dependent excitation is possible for short, <1 ns, CO/sub 2/ laser pulses. Longer pulses exhibit intensity effects. The importance of the breakdown of rotational selection rules to the IRMPE of highly excited NO/sub 2/ is shown.

• Research Organization: Harvard Univ., Boston, MA (USA)
• OSTI ID: 5471092
• Country of Publication: United States
• Language: English

Related Subjects

640304* -- Atomic
Molecular &amp; Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
CARBON DIOXIDE LASERS
CHALCOGENIDES
COLLISIONS
DATA
DEUTERIUM COMPOUNDS
DISSOCIATION
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EXCITATION
EXCITED STATES
EXPERIMENTAL DATA
GAS LASERS
HYDRIDES
HYDROGEN COMPOUNDS
INFORMATION
LASERS
MOLECULE COLLISIONS
NITRIDES
NITROGEN COMPOUNDS
NITROGEN OXIDES
NITROUS OXIDE
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PHOTON COLLISIONS
PHOTON-MOLECULE COLLISIONS
PNICTIDES
SELECTION RULES
SULFUR COMPOUNDS
SULFUR DIOXIDE
SULFUR OXIDES
VIBRATIONAL STATES