BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Energy transfer and quantum effects on rate processes - John Ellis
DTSTART:20150303T210000Z
DTEND:20150303T213000Z
UID:TALK57600@talks.cam.ac.uk
CONTACT:Paulina Rowicka
DESCRIPTION:One of the holy grails of science is to work out how fast atom
 s and molecules "change" what they do - react to make new compounds\, adso
 rb/desorb from a surface or diffuse from the proverbial A to B. The theore
 tical ground work was laid in the 1930's (transition state theory) and 194
 0's (work of Kramer's on the effect of energy transfer rates) and has sinc
 e generated a mountain of papers - yet there are very few experiments that
  can measure rates accurately enough to evaluate these theories as you nee
 d to extrapolate the data from normal time scales (seconds) to timescales 
 12 orders of magnitude smaller. The helium spin echo (HeSE) technique howe
 ver makes possible measurements on the ideal\, fast timescales\, and so th
 e data it yields can be used almost uniquely to test these theories and in
  this talk I will demonstrate that the current almost total reliance on tr
 ansitions state theory can lead to very significant errors in the predicti
 on or rates\, particularly for multistage processes and show HeSE can be u
 sed to quantify the rates of energy transfer that have a controlling influ
 ence on the motion. The technique also allows processes where quantum mech
 anical effects dominate "tunnelling" (particles go where classical mechani
 cs would forbid them) and "effective masses" (particles move as though the
 y were much heavier than they are)\, and\, after a crash course in quantum
  mechanics\, I will present a simple scheme for including these effects in
 to rate theory\, using the "band structure" of the particle states on a su
 rface. It is widely expected that hydrogen\, the lightest atom will show t
 hese effects\, but I will present data that shows that light molecules suc
 h as methane and carbon monoxide can also show the (high) "effective mass"
  effect that will significantly affect the rate of diffusion.
LOCATION:Bateman Room\, Gonville &amp\; Caius College
END:VEVENT
END:VCALENDAR