Journal of Chemical Physics, Vol.105, No.5, 1770-1777, 1996
Midinfrared Spectra of the Proton-Bound Complexes Ne-N-Hco+ (N=1,2)
The nu(1) band of Ne-HCO+ has been recorded for both Ne-20 and Ne-22 containing isotopomers by means of infrared photodissociation spectroscopy. The rotational structure of the band is consistent with a parallel Sigma-Sigma type transition of a linear proton-bound complex. The following constants are extracted for Ne-20-HCO+ : nu(0) = 3046.120+/-0.006 cm(-1), B"=0.099 54+/-0.000 05 cm(-1), D" = (5.30+/-0.30) X 10(-7) cm(-1), H"=(1.1 +/- 0.9) X 10(-11) cm(-1), B’ = 0.100 03+/-0.000 05 cm(-1), D’=(4.89+/-0.30) x 10(-7) cm(-1), H’=(1.6+/-0.9) X 10(-11) cm(-1). The nu(1) band is redshifted by 42.5 cm(-1) from the corresponding nu(1) transition of free HCO+ indicating that the Ne atom has a pronounced influence on the proton motion. Linewidths for individual rovibrational transitions an laser bandwidth limited, demonstrating that the lifetime of the nu(1) level is at least 250 ps. An approximate radial potential for the collinear Ne ... HCO+ interaction is constructed by joining the mid-range potential obtained from a Rydberg-Klein-Rees inversion of the spectroscopic data to the theoretical long-range polarization potential. Based on this potential, the estimated dissociation energy (D-0) for Ne-HCO+ is 438 cm(-1) in the (000) state and 454 cm(-1) in the (100) excited state. The rotationally unresolved nu(1) band of Ne-20(2)-HCO+ is slightly blueshifted with respect to that of Ne-20-HCO+. The observed frequency shift is compatible with a trimer structure where the second Ne atom is attached to the linear Ne-HCO+ dimer core.