Angular dependence of internal energy distributions of activated Fe(CO) sub 5 sup sm bullet + and W(CO) sub 6 sup sm bullet + ions. The contributions of vibrational and electronic excitation mechanisms in kiloelectron volt collisions

• Published in: Journal of the American Chemical Society 1990-01, Vol.112:1
• Main Authors: Horning, S.R., Vincenti, M., Cooks, R.G.
• Format: Article
• Language: English
• Subjects: 360204 > Ceramics, Cermets, & Refractories-- Physical Properties; ANGULAR CORRELATION; COLLISIONS; COMPLEXES; CORRELATIONS; DATA; DATA ANALYSIS; DISSOCIATION; ENERGY LEVELS; ENERGY RANGE; EXCITED STATES; EXPERIMENTAL DATA; INFORMATION; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; IRON COMPLEXES; KEV RANGE; KEV RANGE 01-10; MATERIALS SCIENCE; MEASURING INSTRUMENTS; MEASURING METHODS; NUMERICAL DATA; TRANSITION ELEMENT COMPLEXES 400201 > Chemical & Physicochemical Properties; TUNGSTEN COMPLEXES
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja00157a019

The average internal energy deposited into Fe(CO){sub 5}{sup {sm bullet}+} upon kiloelectron volt collision-induced dissociation (CID) using Ar as a target gas increases with both the collision energy (E) and the angle ({theta}) through which the collision products are collected. An average energy of 7-8 eV is deposited into the Fe(CO){sub 5}{sup {sm bullet}+} ion as it is scattered through a laboratory scattering angle of 2{degree} in a 3-keV collision with Ar. Similar average internal energies are deposited into W(CO){sub 6}{sup {sm bullet}+} at corresponding laboratory scattering angles, the smaller center-of-mass collision energy E{sub cm} for W(CO){sub 6}{sup {sm bullet}+} being compensated for by a larger value of {theta}{sub cm}, making the scattering parameter, (E{theta}){sub cm}, similar for both systems. Collision activation experiments performed with He and C{sub 9}F{sub 20} as target gases show that the effective mass of the latter is much less than its molecular weight, suggesting that the target is internally excited and/or that parts of the target are spectators during collisional activation. The distribution P({epsilon}) of internal energies acquired upon collisional activation is dependent upon the collision energy, the scattering angle, and the nature of the collision gas. The distributions are typically Gaussian in shape at 1.5- and 2-keV collision energies for scattering angles in the range 1 to 2{degree} for the title projectiles. In contrast, distributions for ions scattered through similar angles upon 3-keV collisions are distinctly bimodal in shape. The lower energy component in the bimodal distribution is thought to be due to electronic excitation, while the higher energy component is associated with a vibrational excitation mechanism, as suggested by comparison with energy distributions obtained for electron impact, low-energy collision-activation, and surface-induced dissociation.