Infrared Spectroscopic Investigation of Magic Number Hydrated Metal Ion Clusters Jordan Beck, Jim Lisy June 22,2009 OSU International Symposium on Molecular Spectroscopy

Overview of Presentation  Experimental Setup  Brief History of Magic Number Cluster Ions  Identifying Magic Number Clusters  Spectral Observations of Free-OH Peaks  Spectral Observations of H-bonded Peaks  Conclusions

Experimental Overview Ion Gun Conversion Dynode/ Electron Multiplier Electrostatic Lenses Conical Nozzle Ion Deflector Ion Selecting Quadrupole Mass Filter Ion Guiding Quadrupole Ion Guide Ion Analyzing Quadrupole Mass Filter Source Chamber Detection Chamber Skimmer Ion Guiding Octapole Ion Guide Ion Guiding Chamber Continuum Surelite II-10 Hz Nd 3+ :YAG (1064 nm) Tunable LaserVision OPO/A

Magic Numbers – Brief History  Clusters that appear with large intensity compared to neighbors in Mass Spectra A Note On Terminology Protonated water clusters reported interchangeably as H + (H 2 O) m and H 3 O + (H 2 O) n For consistency, whenever necessary, I have altered the reported index to conform to the H 3 O + (H 2 O) n style Sin-Shong, L., Detection of Large Water Clusters by a Low rf Quadrupole Mass Filter. Review of Scientific Instruments, (4): p

More Magic Numbers Castleman: Hydrated Alkali Metal Ion Magic Numbers Mass Spectral Results Reproducible in Lisy Lab Initial Interpretation: Water Cages Steel, E.A., et al. The Journal of Physical Chemistry, (19): p Number of Water Molecules n

1.Anomalies in mass spectra 2.Anomalies in fragmentation vs. cluster size data Wu, C.-C., et al., Protonated clathrate cages enclosing neutral water molecules: H + (H 2 O) 21 and H + (H 2 O) 28. Journal of Chemical Physics, (7). Identifying Magic Numbers H 3 O + (H 2 O) n

Two Types of Magic Numbers Proposed Magic number n produced primarily by instability of n+1 cluster Magic number n produced by instability of n+1 cluster AND stability of n cluster Rb + (H 2 O) n Number of Water Molecules n K + (H 2 O) n % Fragmentation Li + (H 2 O) n Number of Water Molecules n H 3 O + (H 2 O) n % Fragmentation

1.Anomalies in mass spectra 2.Anomalies in fragmentation vs. cluster size data Identifying Magic Numbers 3.Signatures in IR spectra

DDA, AAD, and AD Peaks H 3 O + (H 2 O) n n=17 n=20 n=21 n=20 AAD AD Shin, J.W., et al., Infrared Signature of Structures Associated with the H+(H2O)n (n = 6 to 27) Clusters. Science, (5674): p AD = Single Acceptor, Single Donor AAD = Double Acceptor, Single Donor n=19 DDA

Investigating Free OH in Magic Clusters Frequency (cm -1 ) Cross Section (arb. units) IRPD of M + (H 2 O) 10 H3OH3O Li Na K Rb Cs IRPD of H 3 O + (H 2 O) n Frequency (cm -1 ) Cross Section (arb. units) n=21 n=20 n=19 n=17 n=10 Cross Section (arb. units) Frequency (cm -1 ) IRPD of Li + (H 2 O) n n=22 n=20 n=18 n=15 n=12 n=10 Cross Section (arb. units) Frequency (cm -1 ) IRPD of Na + (H 2 O) n n=20 n=19 n=18 n=14 n=12 n=10

Investigating Free OH in Magic Clusters Observations 1.Magic H 3 O + (H 2 O) 20 and Li + (H 2 O) 20 have more intense AAD peaks than AD peaks 2.Non-magic and anti- magic clusters also show a preference for AAD-type waters 3.Our results indicate that the disappearance of AD peak not a sensitive indicator of magic number clusters IRPD of H 3 O + (H 2 O) n Frequency (cm -1 ) Cross Section (arb. units) n=21 n=20 n=19 n=17 n=10 AAD/AD * ±0.1 ±0.5 ±0.1 ±0.2 ±1.7 Frequency (cm -1 ) IRPD of Li + (H 2 O) n n=22 n=20 n=18 n=15 n=12 n= ±0.1 ±0.2 ±0.6 AAD/AD * Frequency (cm -1 ) IRPD of Na + (H 2 O) n n=20 n=19 n=18 n=14 n=12 n= ±0.2 ±0.3 ±1.5 ±1.3 ±1.6 AAD/AD * * - Origin 7.5 software used to fit peaks to Lorentzian curves. AAD/AD is the ratio of integrated peak areas.

Shin, J.W., et al. Science, (5674): p Miyazaki, M., et al. Science, (5674): p H 3 O + (H 2 O) 19 H 3 O + (H 2 O) 20 H 3 O + (H 2 O) 21 H 3 O + (H 2 O) 20 Wu, C.-C., et al. Journal of Chemical Physics, (7). Temperature 1.Cluster melting temperature ~ K 2.Chang’s warmest (T~150K) clusters show most prominent magic behavior 3.Lisy clusters even warmer (~200K) than Chang’s, yet magic numbers persist 4.This is evidence against the importance of dodecahedral cages giving rise to magic numbers Temperature

Investigating DDA Peak in Magic Clusters 1.DDA peaks are a promising lead 2.DDA peak apparent in magic, non-magic, and anti-magic clusters Frequency (cm -1 ) IRPD of Na + (H 2 O) n n=20 n=19 Cross Section (arb. units) IRPD of K + (H 2 O) n n=20 n=15 Frequency (cm -1 ) Cross Section (arb. units) IRPD of Rb + (H 2 O) n n=21 Frequency (cm -1 ) Cross Section (arb. units) n=20 n=15 Frequency (cm -1 ) H 3 O + (H 2 O) n n Shin, J.W., et al. Science, (5674): p

Conclusions  Found evidence of two separate types of magic numbers  Presence/absence of AD peak does not seem to be an indicator of magic numbers  DDA peaks observed in magic, non-magic, and anti-magic clusters  Results indicate dodecahedral cages not the most important factor in forming magic clusters  Search for a unique spectral signature for magic number clusters still open for further exploration

Acknowledgements  Professor Jim Lisy  Lisy Lab Jason Rodriguez Amy Nicely Oscar Rodriguez  Funding: NSF CHE NSF CHE

Ion Selecting Quadrupole Mass Filter Ion Guiding Quadrupole Ion Guide Ion Analyzing Quadrupole Mass Filter Detection Chamber Continuum Surelite II-10 Hz Nd 3+ :YAG (1064 nm) Tunable LaserVision OPO/A Experimental Overview Typical Experiment 1) Select cluster ion of interest in first quadrupole (Q1), e.g. Cs + (H 2 O) 20 2) Laser interaction in second quadrupole (Q2) 3) Third quadrupole (Q3) set to monitor loss of most labile ligand, e.g. Cs + (H 2 O) 19 The Solution 3) Third quadrupole (Q3) set to monitor multiple ligand loss channels, e.g. Cs + (H 2 O) 17,18 First two steps are the same The Problem The loss of one water in the typical experiments leads to large background in large clusters due to spontaneous evaporation