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Scientists produce best image yet of atoms moving in real time

April 17, 2013

TORONTO, ON – Call it the ulti­mate nature doc­u­men­tary. Sci­en­tists at the Uni­ver­si­ty of Toron­to have record­ed atom­ic motions in real time, offer­ing a glimpse into the very essence of chem­istry and biol­o­gy at the atom­ic lev­el.

Their record­ing is a direct obser­va­tion of a tran­si­tion state in which atoms under­go chem­i­cal trans­for­ma­tion into new struc­tures with new prop­er­ties – in this case the trans­fer of charge lead­ing to metal­lic behav­iour in organ­ic mol­e­cules. It is described in a study report­ed in the April 18 issue of Nature.

“It’s the first look at how chem­istry and biol­o­gy involve just a few key motions for even the most com­plex sys­tems,” says U of T chem­istry and physics pro­fes­sor R. J. Dwayne Miller, prin­ci­pal inves­ti­ga­tor of the study. “There is an enor­mous reduc­tion in com­plex­i­ty at the defin­ing point, the tran­si­tion state region, which makes chem­i­cal process­es trans­ferrable from one type of mol­e­cule to anoth­er. This is how new drugs or mate­ri­als are made.”

Miller, who holds a joint appoint­ment as direc­tor of the Max Planck Research Group for Struc­tur­al Dynam­ics at the Cen­tre for Free Elec­tron Laser Sci­ence, con­duct­ed the research with col­leagues from insti­tu­tions in Ger­many and Japan. He says nature uses this reduc­tion prin­ci­ple at tran­si­tion states to breathe life into oth­er­wise inan­i­mate mat­ter.

“Imag­ine the com­plex­i­ty of all the enor­mous num­ber of pos­si­ble arrange­ments of atoms in DNA or any oth­er bio­log­i­cal­ly active mol­e­cule. It always does the same thing to dri­ve a bio­log­i­cal func­tion. We can now see how all these pos­si­ble motions become coerced along a par­tic­u­lar path­way by a dom­i­nant play­er.”

To help illu­mi­nate what’s going on here,  Miller explains that with two atoms there is only one pos­si­ble coor­di­nate or dimen­sion for fol­low­ing the chem­i­cal path­way. With three atoms, two dimen­sions are now need­ed. How­ev­er, with a com­plex mol­e­cule, it would be expect­ed that hun­dreds or even thou­sands of dimen­sions would be required to map all pos­si­ble tra­jec­to­ries of the atoms.

“In this case, chem­istry would be a com­plete­ly new prob­lem for every mol­e­cule,” says Miller. “But some­how there is an enor­mous reduc­tion in dimen­sions to just a few motions, and we are now able to see exact­ly how this works at the atom­ic lev­el of detail.”

The result builds on a mile­stone Miller and some for­mer grad­u­ate stu­dents first reached a decade ago.

“One of the long­stand­ing dream exper­i­ments is to direct­ly observe atom­ic motions dur­ing the defin­ing moments that lead to struc­ture change, and we were able to watch sim­ple phase tran­si­tions at the atom­ic lev­el back in 2003,” says Miller. “This led to a new under­stand­ing that now allows for min­i­mal­ly inva­sive laser surgery. It’s a tes­ti­mo­ny to the impor­tance of basic sci­ence and nev­er know­ing where new under­stand­ings will lead.”

“The first atom­ic movies were very grainy, much like the first motion pic­tures,” says Miller. “The new movies are so clear one could dare say they are becom­ing beau­ti­ful to behold, espe­cial­ly when you remem­ber you are look­ing at atoms mov­ing on the fly. We’ve cap­tured them at an incred­i­bly fast rate of less than 1 mil­lionth of a mil­lionth of a sec­ond per frame.”

The break­through was based on the devel­op­ment of ultra-bright elec­tron sources that dates back to the 2003 work.

“Oth­er researchers use x‑rays to cap­ture atom­ic motions, so no one thought we could ever devel­op a bright enough source based on elec­trons as they under­go elec­tron-elec­tron repul­sion and would blow up with­out being able to cap­ture an image on the incred­i­bly short time scale required,” says Miller. “We found a way to coerce the elec­trons into an ultra-short pulse suf­fi­cient­ly bright to lit­er­al­ly light up atom­ic motions as they occur.”

“Elec­trons inter­act with atoms 1 mil­lion times stronger than x‑rays and can be pro­duced with a table-top instru­ment to effi­cient­ly pro­duce enor­mous, effec­tive bright­ness for view­ing atom­ic motions.”

Fund­ing for this research was pro­vid­ed by the Nat­ur­al Sci­ences and Engi­neer­ing Research Coun­cil of Cana­da and the Cana­da Foun­da­tion for Inno­va­tion. Addi­tion­al sup­port was pro­vid­ed by the Max Planck Soci­ety in Ger­many, a Grant-in-Aid for Sci­en­tif­ic Research on Inno­v­a­tive Areas and the G‑COE pro­gram for the field of Chem­istry from The Min­istry of Edu­ca­tion, Cul­ture, Sports, Sci­ence and Tech­nol­o­gy in Japan, and by Cre­ative Sci­en­tif­ic Research from The Japan Soci­ety for the Pro­mo­tion of Sci­ence.

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Note to media: Vis­it to view a sim­u­la­tion of the research described here.


R.J. Dwayne Miller
Depart­ment of Chem­istry
Uni­ver­si­ty of Toron­to

Sean Bet­tam
Fac­ul­ty of Arts & Sci­ence
Uni­ver­si­ty of Toron­to