Ultra-fine metal particle formation via pulsed laser breakdown of carbonyl vapors
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Communications Ultra-Fine Metal Particle Formation via Pulsed Laser Breakdown of Carbonyl Vapors CLIFTON W. DRAPER High power CO2 TEA ( t r a n s v e r s e l y excited a t m o s pheric) l a s e r s a r e capable of sufficient l a s e r power d e n s i t y (W/cm 2) to induce d i e l e c t r i c breakdown of i r r a d i a t e d g a s e s . This " o f f - r e s o n a n c e " p r o c e s s is c a u s e d by a p l a s m a s p a r k g e n e r a t e d in the v e r y high intensity e l e c t r o m a g n e t i c field of the focused p u l s e . The phenomenon has been known since the e a r l y l a s e r y e a r s , 1,2 but has not r e c e i v e d as much attention as the s i m i l a r p r o c e s s of focused l a s e r p l a s m a detonation at solid s u r f a c e s , a,4 The r e a s o n for this being the r e s e a r c h e m p h a s i s on a r e a s of l a s e r - m a t e r i a l p r o c e s sing .5-9 F o r the most p a r t , gas phase d i e l e c t r i c breakdown has been looked upon as a nuisance by people working in the IR multiphoton, " o n - r e s o n a n c e " l a s e r c h e m i s t r y a r e a . Recently though s e v e r a l r e s e a r c h groups ~~ have s t a r t e d to explore applications of this phenomenon. Ronn 1~ and a s s o c i a t e s have used l a s e r induced d i e l e c t r i c breakdown to make p a r t i c l e s of i r o n f r o m f e r r o c e n e , Fe (Calls)2, molybdenum f r o m the carbonyl, Mo (CO)6, and sulfur f r o m OCS and S F J H 2 . Switzer e t al ~2 have studied breakdown t h r e s h o l d s in f l a m e s . F r e u n d and Danen ~3 have r e m o v e d diborane (B2H6) i m p u r i t i e s f r o m silane (Sill4). Lin and B e r t r a n , ~4 and Bauer e t al ~ have e x p l o r e d l a s e r synthetic c h e m i s t r y applications. This communication d e s c r i b e s the f o r m a t i o n of u l t r a fine (
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