Transition Metal Chemistry in Crossed Beams
Please see our publications page for recent work
 



Introduction:
A crossed molecular beams apparatus is used to  measure the velocity and angular distributions of chemical products from bimolecular reactions of transition metal atoms with small molecules.  The apparatus and its capabilities are described in recent publication. We have recently focussed our attention on studies of the reactions of ground state transition metal atoms with simple hydrocarbons such as ethane, ethylene, and acetylene.  The primary goal of our studies is to understand the role of reactant electronic state, orbital occupancy, and collision energy in chemical reactivity.


A beam of transition metal atoms is produced by laser vaporization using a
Smalley-type source.  A 0.25" diameter metal rod is rotated and translated
in front of the pulsed inert gas beam from a piezoelectrically operated valve.
Below,  the pulsed valve, ablation source and skimmer is shown.




In the figure below, the pulsed valve is removed. A copper rod is in place.  Near skimmer the copper
deposited from the ablation source is evident.




We are using this apparatus to study the reaction dynamics of transition metal atoms with
small molecules in crossed beams.  The beams are crossed at right angles in the main
scattering chamber.  Chemical products from the reaction are scattered over a relatively
wide laboratory angular range.  A small fraction of the products enter the detector, where
they are ionized by either electron impact or by photoionization.  A schematic of the apparatus
is shown below.  Click here to  learn more about how we constructed this apparatus.
 


 
 



We have studied the reactions of a variety of atoms from the 2nd row of the periodic table.
The reactions studied to date include those with alkanes such as methane and ethane, alkenes such as
ethylene, alkynes such as acetylene, and carbonyl-containing molecules such as formaldehyde and
acetaldehyde.   For further information on recent work, please see our publications page.

This fall, we began investigating reactions of small transition metal clusters with simple
hydrocarbons such as acetylene.  A very interesting aspect of this work is that the center of mass
angles associated with reactions of different-sized clusters is appreciably different.  It is therefore
possible to directly measure the size-dependent reactivity of Mx, where x > 1. Since we  have
good mass-resolution and fragmentation is minimal using single photon VUV ionization,  it is
possible to study the chemical products resulting from reactions of different sized clusters as a function
of collision energy.   Stay tuned for new results in this area!



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