ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The photoion–photoelectron coincidence (PIPECO) spectra for (CO)+2 in the wavelength region of 620–990 A(ring) have been obtained at different nozzle stagnation pressures (P0). The ionization energy for (CO)2 to CO+(X˜)⋅CO is determined to be (approximately-less-than)12.73±0.05 eV (974±4 A(ring)), indicating that CO+(X˜)⋅CO is bound by more than 1.29 eV. The PIPECO measurements also provide evidence that CO+(A˜,B˜)⋅CO are bound with dissociation energies 〉0.3 eV. At P0≤200 Torr and a nozzle temperature (T) of 120 K, nozzle expansion conditions which minimize the formation of (CO)n (n≥3), the intensities for the CO+(A˜,B˜)⋅CO PIPECO bands are found to be negligibly small compared to that for the CO+(X˜)⋅CO PIPECO band. This observation supports the conclusion that the excited CO+(A˜,B˜)⋅CO ions are dissociative, with dissociation lifetimes〈42 μs. This conclusion is contrary to that of the preliminary study which is based on the PIPECO spectrum for (CO)+2 measured at P0=350 Torr and T=120 K. Assuming that the radiative lifetimes of CO+(A˜ or B˜) and CO+(A˜ or B˜)⋅CO are identical, we estimate that the dissociation lifetimes for CO+(A˜)⋅CO and CO+(B˜)⋅CO are (approximately-less-than)4 μs and (approximately-less-than)50 ns, respectively.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.456368
