Chemical "Double Slits": Dynamical Interference of Photodissociation Pathways in Water

• Published in: Science (American Association for the Advancement of Science) Vol. 285; no. 5431; pp. 1249 - 1253
• Main Authors: Dixon, R. N., Hwang, D. W., Yang, X. F., Harich, S., Lin, J. J., Yang, X.
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for the Advancement of Science 20.08.1999; American Association for the Advancement of Science; The American Association for the Advancement of Science
• Subjects: Atomic and molecular physics; Atoms; Chemistry; Diffuse spectra; predissociation, photodissociation; Dissociation; Dissociation reactions; Energy; Exact sciences and technology; Freshwater; General and physical chemistry; Geometry; Lasers; Lead; Marine; Molecular biology; Molecular properties and interactions with photons; Molecules; Photochemistry; Photolysis; Photon interactions with molecules; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); Physics; Potential energy; Quantum numbers; Quantum theory; Rotational states; Water; United States; Water; Potential energy surfaces; Lambda type doubling; Vibronic states; Triatomic molecule; Inorganic compound
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.285.5431.1249

Photodissociation of water at a wavelength of 121.6 nanometers has been investigated by using the H-atom Rydberg tagging technique. A striking even-odd intensity oscillation was observed in the OH(X) product rotational distribution. Model calculations attribute this oscillation to an unusual dynamical interference brought about by two dissociation pathways that pass through dissimilar conical intersections of potential energy surfaces, but result in the same products. The interference pattern and the OH product rotational distribution are sensitive to the positions and energies of the conical intersections, one with the atoms collinear as H-OH and the other as H-HO. An accurate simulation of the observations would provide a detailed test of global H$_2$O potential energy surfaces for the three (X̃/Ã/B̃) contributing states. The interference observed from the two conical intersection pathways provides a chemical analog of Young's well-known double-slit experiment.