Table of Contents
Laser Chemistry
Volume 7, Issue 1, Pages 35-40

Multiphoton Ionization of Formaldehyde: Observation of 3py and 3pz Rydberg States

Exxon Research and Engineering Company, Route 22 East, Annandale 08801, New Jersey, USA

Received 28 April 1986; Accepted 22 July 1986

Copyright © 1987 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Multiphoton ionization (MPI) of CH2O and CD2O is reported for dye laser wavelengths between 445 and 470 nm. The ionization pathway starts with three-photon resonant absorption to 3py and 3pz Rydberg states. One or two additional photons are required, depending on wavelength, to reach threshold. MPI spectra agree well with VUV absorption measurements of the same Rydberg levels. MPI yields are small and photoacoustic measurements imply the initial three-photon excitation has low probability. Transitions at the four-photon ionization threshold show larger cross sections than the (overall) five-photon ionization bands but hot band transitions were not observed following selective vibrational excitation of ground state molecules.