Photoelectron spectroscopic and theoretical study of ketene imine, CH2=C=NH, and ketene N-methylimine, CH2=C=NCH3

Article abstract of DOI:10.1021/ja00166a011

The organic transient molecule ketene imine, CH₂=C=NH, which may be important to the chemistry of the interstellar medium, has been produced by thermolysis of 3-hydroxypropionitrile, HOCH₂CH₂CN, and its He I photoelectron spectrum obtained for the first time. The interpretation of the spectrum is assisted by the calculation of the lowest four vertical ionization energies by a recently developed ab initio multireference coupled-cluster method (MRCC) and the SCF calculation of the vibrational frequencies of the lowest two cationic states. The lowest three observed ionization energies are 9.28, 11.91, and 13.04 eV. A fourth ionization is observed in the range 15-16 eV, but precise measurement is not possible because of contamination of this region of the spectrum by formaldehyde. The MRCC calculations predict ionization energies of 9.18 (a′), 12.03 (a″), 13.17 (a′), and 15.68 (a″) eV. Additional experimental and MRCC results for ketene N-methylimine, CH₂=C=NCH₃, provide further confirmation of the assignments for ketene imine.