Dependence on scattering angle of the internal energy distribution of products of charge‐changing collisions

Abstract

The internal energy distributions arising from chargechanging collisions were measured as a function of scattering angle, 0, for the 'thermometer' molecule W(CO),. The experiments were performed by modifying a reversegeometry mass-analyzed ion kinetic energy (MIKE) spectrometer by adding angle-resolving slits which aUow measurement of the scattering angle in the non-focusing plane of the instrument. Charge exchange of W(C0):' with benzene to give W(CO):' , a d charge stripping of W(C0):' on collision with O2 to give W(CO)i+, were studied at 6 keV with the product ions being c o k t e d over hboratory scattering angles selected in the range 0-0.60 ' . Tbe results show that charge-chaaging collisions accompanied by scattering have the potential for depositing extremely large internal energies. The observation of the W(C0)" ion formed in dissociative charge stripping of W(C0):'shows that it is possible to deposit at least 27 eV into the colliding W(C0);. ion; of this energy, 15 eV is d for the cbargwtripping process, leaving 12 eV of internal energy in the nascent W(CO):+*. Even greater internal energies (more than 15 ev) can be deposited into scattered W(CO):' * prodwed by charge exchange of the doubly charged ion. The availability of such high internal energies has potential use in causing dissociation of refractory ions such as those of biomolecules. The average internal energy, eAVE, deposited increases with the scattering angle at a rate of 10 eV degree-' for charge exchange, and at approximately 5 eV degree-' for charge stripping and for simple collision-induced dissociation (CID). This observation suggests that Don-Zero angle charge stripping and CID may occur via similar mechanisms in which direct vibrational activation occurs in small impact parameter collisions which also lead to angular scattering. The higher internal energies and larger 8~y~ YS. 8 dependence observed for charge exchange are consistent with the formation of the products upon a highly repulsive surface associated with coulombic repulsion between the separating products.

Theoretical Study of Tungsten Carbonyl Complexes (n = 1−6): Structures, Binding Energies, and Implications for Gas Phase Reactivities

“…In cases such as metal carbonyls, where all fragmentation processes (or nearly so) are simple bond cleavages, knowledge of the successive (CO) n -1 W + −CO binding energies enables one to derive distributions of internal energies on the basis of the relative intensities of fragments (0 ≤ n ≤ 6). This has lead to a wealth of information about several activation processes such as low- and high-energy collision-induced dissociation (CID), electron-induced dissociation (EID), neutralization−reionization (NRMS), and charge exchange processes . These analyses rely on binding energies which have been obtained as appearance potentials for the successive fragments, when neutral W(CO) 6 is subjected to the impact of accelerated electrons …”