Articles you may be interested inHigh resolution photoelectron spectroscopy and femtosecond intramolecular dynamics of H2CCO+ and D2CCO+ J. Chem. Phys. 99, 2520 (1993); 10.1063/1.465215High resolution photoelectron spectroscopy and femtosecond intramolecular dynamics of H2CO+ and D2CO+The 584 A photoelectron spectra of supersonic molecular beams of H 2 0 and D 2 0 have been obtained with improved resolution. The spectroscopic constants of the X 2 Bland A 2A I state ions, including w? , x? I , w~, X~2' and X?l' are reported. For the first two electronic states of the ion, precise line splittings were evaluated with a least squares fitting procedure, employing sums of empirical instrument response functions and a linear background. A simulation of the vibrational manifolds of the B 2 B2 state ions with combination progressions in the symmetryallowed modes VI and V 2 failed to reproduce the diffuse photoelectron bands observed for both H 2 0 and D 2 0. Autocorrelation functions were calculated from the photoelectron bands of all three electronic states. The B 2Bl state correlation functions exhibit ultrafast decay, occurring on a 10-14 s time scale. The V 2 motion appears to define the decay in the correlation function.This behavior supports a previously proposed B 2B2-A 2AI curve-crossing model for the nonradiative relaxation ofthe B 2B2 state ions.the 600-1000 A region revealed that the threshold for frag-6928
The 584 Å photoelectron spectra of rotationally cold C2H2 and C2D2 were obtained with improved resolution, permitting the first three electronic states of the ions to be characterized in greater detail. Temperature-dependent studies led to a definitive assignment of the low intensity features in the X̃ 2∏u state, yielding ν4=837±12 cm−1 for C2H+2 and ν4=702±12 cm−1 for C2D+2. The ν5 origin of the Renner–Teller multiplet was identified. In the case of C2D+2, a Fermi resonance with this multiplet contributed intensity to the ν1 mode, facilitating its evaluation at 2572±16 cm−1. The C2h geometry of the à 2Ag state was determined from the two previously unobserved bending progressions, assigned to ν4 and ν5B, and evaluated at 492±12 and 605±12 cm−1 for C2H+2 and 339±12 and 516±12 cm−1 for C2D+2, respectively. A more extensive vibrational progression than previously evident, comprised of irregular spectral features indicative of nonadiabatic effects, was observed for the B 2∑+u state. Autocorrelation functions were derived from the spectra for all three electronic states, and the two electronically excited states exhibit an ultrafast decay on a 10−14 s time scale. The à 2Ag state decays within one period of bending vibration, while the B̃ 2∑+u state survives only 14 fs, corresponding to a single period of symmetric stretching motion.
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