Study of photoexcited states by positron method. Final report

Technical Report · Thu Jan 01 00:00:00 EST 1981

DOI:https://doi.org/10.2172/5633215· OSTI ID:5633215

Positrons can be used as markers in microscopic studies of molecular systems. This is so because positrons, as antiparticles of electrons, will annihilate with an electron in the medium under conditions that signify the electron density and momenta at the site of the positron. In most insulators, positrons can capture an electron into a stable atomic state before annihilation called positronium (Ps). Positronium, when formed, is a particularly powerful probe of materials since Ps annihilates in distinct ways from free positrons. It also has two different spin states which can be perturbed by paramagnetic centers in the medium and, thereby, measure their concentration and properties. This aspect of low-energy positron physics was taken advantage of for the study of light-excited electronic states in organic molecules. Long-lived triplet states, which normally yield phosphorescent luminescence on deexcitation, are particularly interesting. The triplet state has long been the subject of speculation as to its role in biology, the transmission of information, distribution of photo and radiation effects, etc. It was the object of this project to assess the potential of the positron method for the detection of trace concentrations of photo-induced triplet states of organic molecules. Progress is discussed. (WHK)

• Research Organization: New York Univ., NY (USA). Dept. of Physics
• DOE Contract Number: AS02-77EV04500
• OSTI ID: 5633215
• Report Number(s): DOE/EV/04500-2; ON: DE82005469
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ORGANIC COMPOUNDS
ELECTRON-POSITRON INTERACTIONS
EXCITED STATES
POSITRONIUM
ANNIHILATION
CROSS SECTIONS
DE-EXCITATION
EXCITATION
MOLECULES
PHOTON-MOLECULE COLLISIONS
SPIN FLIP
TRIPLETS
BASIC INTERACTIONS
COLLISIONS
ELECTROMAGNETIC INTERACTIONS
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
INTERACTIONS
LEPTON-LEPTON INTERACTIONS
MOLECULE COLLISIONS
MULTIPLETS
PARTICLE INTERACTIONS
PHOTON COLLISIONS
640303* - Atomic
Molecular & Chemical Physics- Positronium
Muonium
& Muonic & Mesic Atoms & Molecules