Photoionization mass spectrometric study of formaldehyde H$sub 2$CO, HDCO and D$sub 2$CO
Photoionization efficiency curves for H$sub 2$CO$sup +$, HDCO$sup +$, D$sub 2$CO$sup +$ and HCO$sup +$, DCO$sup +$ and CO$sup +$ fragment ions are obtained. The ionization potentials of H$sub 2$CO, HDCO, and D$sub 2$CO thus determined are, respectively, 10.86$sub 8$, 10.87$sub 9$, and 10.88$sub 2$ eV. The appearance potential of HCO$sup +$ fragment is observed at 11.92+-0.01 eV, from which the dissociation energy of H$sub 2$CO$sup +$, the proton affinity of CO, and the ionization potential of HCO are inferred. The heat of formation $delta$Hf$sup 0$$sub 0$ (HCO$sup +$) =196.2+-0.5 kcal/mole is obtained, a value lower than any one previous determination. From the abundance ratios measurements the variation of the mass spectrum with photon energy is determined, and hydrogen isotope effects are measured. The observation of a metastable transition (D$sub 2$CO$sup +$)/subm/$Yields$DCO$sup +$+D with a threshold some 2 eV above the dissociation limit is discussed along with the dissociation mechanisms with the help of correlation diagrams. Finally, the finer structure in the photoionization efficiency curves is analyzed in terms of preionized Rydberg series converging to the second and third electronic state of the ion. (AIP)
- Research Organization:
- Argonne National Laboratory, Argonne, Illinois 60439
- NSA Number:
- NSA-33-025423
- OSTI ID:
- 4025988
- Journal Information:
- J. Chem. Phys., v. 64, no. 4, pp. 1419-1436, Journal Name: J. Chem. Phys., v. 64, no. 4, pp. 1419-1436; ISSN JCPSA
- Country of Publication:
- United States
- Language:
- English
Similar Records
Reaction of fluorine and chlorine atoms with formaldehyde and deutero-formaldehyde
T/sub 1/ barrier height, S/sub 1/--T/sub 1/ intersystem crossing rate, and S/sub 0/ radical dissociation threshold for H/sub 2/CO, D/sub 2/CO, and HDCO