Multiphoton ionization as a probe of molecular photofragmentation: statistical and dynamical energy partitioning in the multiphoton dissociation of nitromethane

Thesis/Dissertation · Fri Jan 01 00:00:00 EST 1982

OSTI ID:6248030

Rockney, B H

Multiphoton ionization (MPI) appears in its first use as a probe of laser-induced photofragmentation. Specifically, MPI here reveals the internal and translational energy content of the nascent fragments from the infrared multiphoton dissociation (MPD) of nitromethane (CH/sub 3/NO/sub 2/). The apparatus for this work consists of a pulsed supersonic molecular beam crossed by two pulsed and focused lasers - a CO/sub 2/ laser to induce collision-free unimolecular dissociation of CH/sub 3/NO/sub 2/, and a tunable dye laser following immediately to ionize selectively one of the pair of dissociation fragments for detection by a mass spectrometer and particle multiplier. A computer simulation of each fragment's MPI spectrum, a series of four photon resonances to members of the npsigma/sub u/ Rydberg state of NO/sub 2/ and three photon resonances to two vibrational members of the ..gamma../sub 1/ Rydberg state of CH/sub 3/, aids in determining the fragment's internal energy content. The dye laser is delayed and its focus is traced through a small quarter circle centered at the focus of the CO/sub 2/ laser. The flight times of the fragments from the point of dissociation and their laboratory scattering angular distributions at fixed ionizing laser wavelength provide their center of mass recoil velocity distributions. The energy deposited in the fragments evidences a striking mixture of statistical and dynamical energy partitioning. The statistical RRKM theory of unimolecular decomposition accurately predicts the amount of internal energy found in the fragments.

• Research Organization: Cornell Univ., Ithaca, NY (USA)
• OSTI ID: 6248030
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
NITROMETHANE
DISSOCIATION
CARBON DIOXIDE LASERS
COMPUTERIZED SIMULATION
DECAY
DYE LASERS
IONIZATION
MOLECULAR BEAMS
MULTI-PHOTON PROCESSES
RYDBERG STATES
BEAMS
CHEMICAL EXPLOSIVES
ENERGY LEVELS
EXCITED STATES
EXPLOSIVES
GAS LASERS
LASERS
LIQUID LASERS
NITRO COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
SIMULATION
640302* - Atomic
Molecular & Chemical Physics- Atomic & Molecular Properties & Theory