SIMULTANEOUS COUNTER-ION CO- DEPOSITION: A TECHNIQUE ENABLING MATRIX ISOLATION SPECTROSCOPY STUDIES USING LOW-ENERGY BEAMS OF MASS-SELECTED IONS Ryan M. Ludwig, David T. Moore Chemistry Department, Lehigh University Bethlehem, PA 18015

Introduction Matrix Isolation  Pimentel Fast energy dissipation Inert chemical environment Kinetic control Study of ions Requires charge balance Intrinsically neutral sources (Plasmas)  Jacox, Andrews High ion beam energies  Maier Controlled co-deposition of anions and cations 2 Whittle, E.; Dows, D. A.; Pimentel, G. C. J. Chem. Phys. 1954, 22, Jacox, M. E.; Thompson, W. E. Res. Chem. Intermed. 1989, 12, Zhou, M.; Andrews, L.; Bauschlicher, C. W. Chem. Rev. 2001, 101, Forney, D.; Jakobi, M.; Maier, J. J. Chem. Phys. 1989, 90,

Ion Optics 3

Optical Beam Path Trial system  Anionic copper carbonyl Deposition Specs Ion current: 10 nA -10 eV Cu - 60 eV Ar + or Kr + Matrix: CO in Ar Matrix flow rate: 27 mmol/hour 2 hour at 10K or 20K Ion abundance 1:10 6 Cu - to Ar 4

Matrix Isolation FTIR Cu - Kr % CO in Ar 2hr deposition at 20K CO in Ar  2138 cm -1 Both anionic and neutral peaks formed upon deposition Annealing  begin neutralizing anionic species Higher temperatures saturate neutral copper center Ludwig, R. M.; Moore, D. T. J. Chem. Phys. 2013, 139, n=1 n=2 n= * * * Zhou, M.; Andrews, L. J. Chem. Phys. 1999, 111, Huber, H.; Kundig, E. P.; Moskovits, M.; Ozin, G. A. J. Am. Chem. Soc. 1975, 97, CO Copper Carbonyl

Concentration Dependence Copper coordination increases with CO concentration Broad feature near anionic tricarbonyl Not large shift from anionic tricarbonyl Cu(CO) 3 - stable 18 electron complex Cu(CO) 3 (CO) n - Total band intensity remains constant across 25-fold range Cu is the limiting reagent 6

10K Deposition No complexation upon deposition Annealing  neutral tricarbonyl appears Free Cu - diffuses to cation center Large energy release upon ion recombination Similar to 0.02% CO at 20K Gives mechanistic insight Faster freezing-out at low temp 7

What leads to Neutralization? 8

Neutralization Events 25K  population transfer from anions to neutrals Higher temps  complexation Neutralization without heating sample 2 qualitatively different neutralization events 9

Conclusions MI of ionic species of interest is facilitated by counter-ion deposition Should be generally applicable Both thermal recombination and photodetachment events lead to neutralization Acknowledgements $$ NSF CHE Lehigh University 10

Cation Comparison Qualitatively similar between Kr + and Ar + Reflective of anionic system 11