UCSB~~

Mechanistic Studies of Laser-Induced NucleationBrandon C. Knott.' Jerry L. LaRue,2 Alec M. Vvodtke.? Michael F. Doherty.' and Baron Peters1,2

"Department of Chemical Engineering , University of California , Santa Barbara , CA, 93106-5080-Department of Chemistry and Biochemistry, University of California , Santa Barbara , CA, 93106-5080

3.0

No arg on

Laser :• A. = 532 nm• 7 ns pulse• 5mm beam

diameter• 5cm vessel

diameterlike NPLINfor crystals

&35S nm (ultmpure)e S32 nm {ultrapurel. S32 nm (lap)• 1064 nm tultrapure)

tap =pure, notsensitive to 'dust'

With argon

I1.5 2.0 2.5

Supersaturation (C!Co:ll)

••••

With laser*:no laser:

Could bubbles cause nucleationof crystals? In argonated waterthat is co-supersaturated withglycine , glycine crystals formhours after argon bubbles arereleased. For the control w ithno argon, glycine rema ins insolution .

the pulse energythat gives 0.1bubbles per pulseover many pulsesis defined as thethreshold pulseenergy.

• Previous investigatiorss.13 found that a minimum pulse intensityis needed to induce nucleation. We show how the thresholddepends onsupersaturation.

Laser-Induced BubbleNucleation Experiments

• To test the hypothesized optical Kerr mechanism for laser-inducedcrystal nucleation (Myerson, Garetz , et al.) we tested whether alaser could induce nucleation of CO 2 bubbles from carbonated w ater

• Cavitation was not observed in laser-induced crystalnucleation experiments by Myerson et aI., but small transientbubbles might not be seen.

• in our experiment ,any nanoscale or larger bubble will grow tobecome a macroscopic bubble and be seen .

• enhanced solute alignment should not help form a CO 2 bubble, soif bubbles form there is a non-Kerr effect at work .

*(right) taken just after a single 7 ns pulse of energy 280 mJ.even if all of the pulse energy is absorbed by the irradiatedzone, the temperature rise of the solution is only 0(10.4) K.

1 Garetz et al. Phys. Rev. Lett. 77,3475 (1996) .2 Garetz et al. Phys . Rev. Lett. 89 ,175501 (2002).3 Sun et al. CNSt. Growth Des. 6, 684 (2001) .4 Lee et al. CNSt. Growth Des . 8, 4255 (2008).5 Alexander and Camp 9Y& Growth Des . 9, 958 (2009) .6 Kofke and Glandt Mol. Phys . 64 , 1005 (1988) .7 Pool and BolhuisJ. Phys . Chern . B 109 , 6650 (2005) .8 Pool and Bolhuis Phys . Chern. Chern . Phys . 8, 941 (2006) .9 Knott et al. J. Chern. Phys. 131, 224112 (2009).10 Erderniret al.Acc. Chern . Res . 42, 621 (2009).11 ten Wolde and Frenkel Science 277 , 1975 (1997) .12 Zaccaro et al. CNSt. Growth Des . 1, 5 (200 1).13 Matic et al. CNSt. Growth Des . 5, 1565 (2005).14 Knott et al. J . Chern. Phys.134, 154501 (2011)15 Knott et al. J. Cehrn . Phys. in press (2011)

ISO

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By classical mechanism?• How does orientational biasinfluence work to form nucleusof size n? In experirnents.t?the oreientational bias is £-10.6

• In PLG model , a much largerorientational bias (s) is requiredfor appreciable barrier reduction .

• Need measure of crystallinity:X=(solid bonds in cluster)

!(total bonds in cluster)

By second step in two-step nucleation?• Can orientational bias facilitate

crystallization of an amorphousnucleus?

• solid bond is a pair of nearest-neighboring solutes withthe same orientation.

(e) 0 Test for effect of induced

NUC=~'I o~ orientational b~as for both

0 (8) ,; 0 0 O'~d0 ~~eChanJsmso 000 0