High-resolution photoionization spectrum of water molecules in a supersonic beam
We have obtained high-resolution (approx.1.5 cm/sup -1/) photoionization spectra of supersonically cooled (T/sub rot/approx.50 K) H/sub 2/O and D/sub 2/O in the 1000--900 A range. The light source, which used the technique of frequency tripling in a pulsed free jet of gas, is described briefly. Spectra are rotationally resolved. Vibrationally excited autoionizing Rydberg series converging to the ground electronic (X; (1b/sub 1/)/sup -1/) state of the molecular ion are detected. This may well be the first example of a highly resolved Rydberg spectrum of a stable polyatomic molecule. From the convergence limit, the ionization potential H/sub 2/O is determined to be 101 777 +- 7 cm/sup -1/. Intensities of the Rydberg state autoionization signals are smaller than predicted with known Franck--Condon factors, indicating that predissociation is a competitive decay channel. Rydberg state lifetimes are approx.1 ps, deduced from homogeneous linewidths. Autoionizing features from Rydberg states associated with the ion's quasilinear A-italic-tilde (3a/sub 1/)/sup -1/ state are observed with linewidths above 10 cm/sup -1/, indicating that their lifetimes are less than approx.0.5 ps. Rotational assignments of some of the bands in this linearreverse arrowbent transition show that the Rydberg and ionic state geometries are nearly identical. A consistent assignment of the controversial bending (v/sub 2/) quantum number and Rydberg series quantum defect delta = -0.037 have been provided.
- Research Organization:
- Materials and Chemical Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5714759
- Journal Information:
- J. Chem. Phys.; (United States), Vol. 88:4
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
HEAVY WATER
IONIZATION POTENTIAL
PHOTOIONIZATION
PREDISSOCIATION
WATER
AUTOIONIZATION
LIFETIME
MOLECULAR BEAMS
RYDBERG STATES
SUPERSONIC FLOW
BEAMS
DISSOCIATION
ENERGY LEVELS
EXCITED STATES
FLUID FLOW
HYDROGEN COMPOUNDS
IONIZATION
OXYGEN COMPOUNDS
640302* - Atomic
Molecular & Chemical Physics- Atomic & Molecular Properties & Theory
640301 - Atomic
Molecular & Chemical Physics- Beams & their Reactions