A photoion-photoelectron coincidence study of (CO) 2 and (CO) 3

The photoion–photoelectron coincidence (PIPECO) spectra for (N2)+2 in the wavelength range 650–866 A have been measured at different nozzle stagnation pressures. The formation of stable (N2)+2 from fragmentation of excited (N2)+n cluster ions initially produced by photoionization of (N2)n, n≥3, is efficient. For nozzle expansion conditions which minimize the production of (N2)n, n≥3, the intensities for the N+2(A,B)⋅N2 PIPECO bands are found to be negligibly small compared to that of the N+2(X)⋅N2 PIPECO band, indicating that the electronically excited N+2(A,B)⋅N2 dimer ions are dissociative in temporal ranges <42 μs. Assuming that the radiative lifetimes for N+2(A,B) and N+2(A,B)⋅N2 are identical, we estimate that the dissociative lifetimes for N+2(A)⋅N2 and N+2(B)⋅N2 are ≲10 μs and ≲60 ns, respectively. The ionization energy for (N2)2 is determined to be 14.50±0.08 eV (855±5 A), suggesting that N+2(X)⋅N2 is bound by 1.09±0.08 eV. The PIPECO data for (N2)+2 presented here and those for (CO)+2...

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