Matrix Isolation Study of the Interaction of Excited Neon Atoms With Allene and Propyne. Infrared Spectra of H2CCCH2+ and H2CCCH-

Published

November 1, 2001

Author(s)

D Forney, Marilyn E. Jacox, C Lugez, Warren E. Thompson

Abstract

When a Ne:allene or a Ne:propyne sample was codeposited at approximately 5 K with a sample of pure neon that had been excited in a microwave discharge to provide a 16.6-16.85 eV energy source, prominent new infrared absorptions which can be assigned to the H₂CCCH₂₊ cation appeared. Also present in the allene experiments were two absorptions which can be assigned to H₂CCCH-. In the propyne experiments, an absorption is tentatively attributed to the strongest infrared fundamental of CH₃CCH⁺. The structures and vibrational fundamentals obtained from density functional and ab initio calculations for various isotopomers of H₂CCCH₂⁺, CH₃CCH⁺, cyc-C₃H₃+, H₂CCCH⁺, and H₂CCCH^- are given. The infrared absorption pattern of the cation common to the allene and propyne experiments matches that of the predominant gas-phase product, cyc-C₃H₃⁺, reasonably well, except for the presence of extra peaks in the CH-stretching region. However, comparison of the results of experiments on isotopically substituted samples with the calculated spectra excludes that assignment and supports the identification of the neon-matrix product as H₂CCCH₂⁺. It is suggested that collisions with the excess of neon atoms in the sampling region rapidly remove excess energy from the initially formed allene and propyne cations, inhibiting the loss of an H atom from those two species.

Citation

Journal of Chemical Physics

Volume

115

Issue

No. 18

Pub Type

Journals

Keywords

ab initio calculations, allene cation, allenyl anion, cyclopropenylium, infrared spectrum, neon matrix, photoionization, propargylium, propyne cation

Citation

Forney, D. , Jacox, M. , Lugez, C. and Thompson, W. (2001), Matrix Isolation Study of the Interaction of Excited Neon Atoms With Allene and Propyne. Infrared Spectra of H₂CCCH₂⁺ and H₂CCCH^-, Journal of Chemical Physics (Accessed April 19, 2024)