Molecular Lightning Rods: Charge Steering during Ionization of the Isomers of HCCCN-HCN and HCCH-HCN in Helium Nanodroplets William K. Lewis, C. Michael Lindsay and Roger E. Miller Department of Chemistry University of North Carolina at Chapel Hill

Ionization Methods Electron impact Photoionization Chemical ionization Field Ionization MALDI Electrospray + +

Ionization Methods Electron impact Photoionization Chemical ionization Field Ionization MALDI Electrospray K. Joutsiniemi,et al., Rapid Commun. Mass Spectrom., 12, 876 (1998). F. Remacle, et al., J. Phys. Chem. A, 103, 10149 (1999). W. C. Stolte, et al., J. Phys. B: At. Mol. Opt. Phys., 35, L253 (2002). M. Thevis, et al., J. Am. Soc. Mass Spectrom. 14, 658 (2003). A. F. Lago, et al., J. Chem. Phys. 120, 9547 (2004).

Charge Transfer Ionization in Helium Droplets Helium atom is ionized by e- impact Charge begins to migrate through the droplet on the femtosecond timescale He+ + n He  He+n+1 He+n+1 is desolvated Charge transfers to dopant and vibrationally hot ion evaporates the droplet. + work of Toennies, Janda, Atkins, Halberstadt, and others

+ - + + Lewis, et al, J. Am. Chem. Soc., 127, 7235 (2005)

Steering Charges with Electrostatic Moments + - IPHe-IPmolecule=10-15 eV T=0.4 K, 1016 K/s cooling rate + -

Steering Charges with Electrostatic Moments + - IPHe-IPmolecule=10-15 eV T=0.4 K, 1016 K/s cooling rate + -

Optically Selected Mass Spectrometry (OSMS) e- impact quadrupole mass spectrometer

Optically Selected Mass Spectrometry (OSMS) e- impact quadrupole mass spectrometer hv

Optically Selected Mass Spectrometry (OSMS) e- impact quadrupole mass spectrometer hv

HCCH  HCCH+ HCN + HCCH+  HCN-H+ + CCH ΔH = -0.4 eV HCN  HCN+ HCCH + HCN+  HCCH-H+ + CN ΔH = -1.3 eV HCCH + HCN+  HCCH+ + HCN ΔH = -2.2 eV HCN+  H + CN+ ΔH = 5.4 eV J. Francisco and S. Richardson, JCP, 101, 7707 (1994)., NIST Webbook, CRC Handbook

+ - + - 3259 cm-1 3235 cm-1 HCN  HCN+ HCCCN + HCN+  HCCCN-H+ + CN ΔH = -2.4 eV HCCCN + HCN+  HCCCN+ + HCN ΔH = -2.0 eV 3259 cm-1 3235 cm-1 HCCCN  HCCCN+ HCN + HCCCN+  HCN-H+ + CCCN ΔH = 0.9 eV J. Francisco and S. Richardson, JCP, 101, 7707 (1994)., NIST Webbook, CRC Handbook

Unfavored product ions [ ]+  HCCCN-H+ HCCCN+ + HCN  HCCCN-H+ + CN ΔE = -0.4 eV HCCCN + HCN+  HCCCN-H+ + CN ΔE = -2.4 eV [ ]+  HCN-H+ HCN+ + HCCCN  HCN-H+ + CCCN ΔE = -1.0 eV HCN + HCCCN+  HCN-H+ + CCCN ΔE = 0.9 eV

Unfavored product ions [ ]+  HCN-H+ HCN+ + HCCH  HCN-H+ + CCH ΔE = -2.5 eV HCN + HCCH+  HCN-H+ + CCH ΔE = -0.4 eV [ ]+  HCCH-H+ HCCH+ + HCN  HCCH-H+ + CN ΔE = 0.9 eV HCCH + HCN+  HCCH-H+ + CN ΔE = -1.3 eV

Summary OSMS spectra have been used to examine the ions formed from various isomers of HCN-HCCH and HCN-HCCCN. The ions observed are consistent with charge steering by the electrostatic moments of the complex. Product ions requiring large amplitude rearrangements are not observed (or only weakly present), suggests rapid cooling and/or caging.

Acknowledgements Jeremy Merritt Paul Stiles Gary Douberly Myong-Yong Choi Travis Falconer Mike Barrett Alessandra Ferzoco Phil Remes Aaron Johnson