Charge transfer and penning ionization of dopants in or on helium nanodroplets exposed to EUV radiation.

Helium nanodroplets are widely used as a cold, weakly interacting matrix for spectroscopy of embedded species. In this work, we excite or ionize doped He droplets using synchrotron radiation and study the effect onto the dopant atoms depending on their location inside the droplets (rare gases) or outside at the droplet surface (alkali metals). Using photoelectron-photoion coincidence imaging spectroscopy at variable photon energies (20-25 eV), we compare the rates of charge-transfer to Penning ionization of the dopants in the two cases. The surprising finding is that alkali metals, in contrast to the rare gases, are efficiently Penning ionized upon excitation of the (n = 2)-bands of the host droplets. This indicates rapid migration of the excitation to the droplet surface, followed by relaxation, and eventually energy transfer to the alkali dopants.

[1]  S. Leone,et al.  Ultrafast probing of ejection dynamics of Rydberg atoms and molecular fragments from electronically excited helium nanodroplets. , 2012, The Journal of chemical physics.

[2]  J. Ullrich,et al.  Evolution of dopant-induced helium nanoplasmas , 2012, 1203.1245.

[3]  M. Mudrich,et al.  Photoionization and imaging spectroscopy of rubidium atoms attached to helium nanodroplets. , 2011, Physical chemistry chemical physics : PCCP.

[4]  S. Leone,et al.  Femtosecond extreme ultraviolet ion imaging of ultrafast dynamics in electronically excited helium nanodroplets , 2012, IEEE Journal of Selected Topics in Quantum Electronics.

[5]  M. Macovei,et al.  Collectively enhanced resonant photoionization in a multiatom ensemble , 2011, 1109.2739.

[6]  T. Märk,et al.  The submersion of sodium clusters in helium nanodroplets: identification of the surface → interior transition. , 2011, The Journal of chemical physics.

[7]  C. Callegari,et al.  Perturbation method to calculate the interaction potentials and electronic excitation spectra of atoms in He nanodroplets. , 2011, The journal of physical chemistry. A.

[8]  T. Möller,et al.  Size and isotope effects of helium clusters and droplets: identification of surface and bulk-volume excitations. , 2011, The journal of physical chemistry. A.

[9]  S. Leone,et al.  Femtosecond photoelectron imaging of transient electronic states and Rydberg atom emission from electronically excited he droplets. , 2011, The journal of physical chemistry. A.

[10]  P. O’Keeffe,et al.  A photoelectron velocity map imaging spectrometer for experiments combining synchrotron and laser radiations. , 2011, The Review of scientific instruments.

[11]  M. Drabbels,et al.  Unusual Rydberg system consisting of a positively charged helium nanodroplet with an orbiting electron. , 2011, Physical review letters.

[12]  B. Najjari,et al.  Two-Center Resonant Photoionization , 2010, Physical review letters.

[13]  Martin Head-Gordon,et al.  Ab initio calculations on the electronically excited states of small helium clusters. , 2010, The journal of physical chemistry. A.

[14]  S. Wüster,et al.  Newton's cradle and entanglement transport in a flexible Rydberg chain. , 2010, Physical review letters.

[15]  Andrew T. Healy,et al.  Ultrafast dynamics in helium nanodroplets probed by femtosecond time-resolved EUV photoelectron imaging. , 2010, Journal of Physical Chemistry A.

[16]  D. Peterka,et al.  Photoelectron imaging of helium droplets doped with Xe and Kr atoms. , 2008, The journal of physical chemistry. A.

[17]  D. Peterka,et al.  Photoionization dynamics in pure helium droplets. , 2007, The journal of physical chemistry. A.

[18]  D. Peterka,et al.  Photoionization and photofragmentation of SF6 in helium nanodroplets. , 2006, The journal of physical chemistry. B.

[19]  D. Peterka,et al.  Photoionization of helium nanodroplets doped with rare gas atoms. , 2006, The Journal of chemical physics.

[20]  F. Stienkemeier,et al.  Spectroscopy and dynamics in helium nanodroplets , 2006, physics/0604090.

[21]  T. Möller,et al.  Electronic and geometric structure of doped rare-gas clusters: surface, site and size effects studied with luminescence spectroscopy , 2006 .

[22]  Gordon W. F. Drake,et al.  High Precision Calculations for Helium , 2006 .

[23]  C. M. Lindsay,et al.  Probing charge-transfer processes in helium nanodroplets by optically selected mass spectrometry (OSMS): charge steering by long-range interactions. , 2005, Journal of the American Chemical Society.

[24]  T. Möller,et al.  The electronically excited states of helium clusters: an unusual example for the presence of Rydberg states in condensed matter , 2005 .

[25]  I. Powis,et al.  Two-dimensional charged particle image inversion using a polar basis function expansion , 2004 .

[26]  R. Bemish,et al.  Electron impact ionization in helium nanodroplets: controlling fragmentation by active cooling of molecular ions. , 2004, Journal of the American Chemical Society.

[27]  J. Toennies,et al.  Superfluid helium droplets: a uniquely cold nanomatrix for molecules and molecular complexes. , 2004, Angewandte Chemie.

[28]  D. Peterka,et al.  Photoelectron imaging of helium droplets. , 2003, Physical review letters.

[29]  T. Möller,et al.  Dissociation and suppressed ionization of H2O molecules embedded in He clusters: The role of the cluster as a cage , 2001 .

[30]  M. Vrakking.  An iterative procedure for the inversion of two-dimensional ion/photoelectron imaging experiments , 2001 .

[31]  T. Möller,et al.  Observation of atomiclike electronic excitations in pure 3He and 4He clusters studied by fluorescence excitation spectroscopy. , 2001, Physical review letters.

[32]  F. Stienkemeier,et al.  Langmuir–Taylor surface ionization of alkali (Li, Na, K) and alkaline earth (Ca, Sr, Ba) atoms attached to helium droplets , 2000 .

[33]  K. Janda,et al.  Charge transfer and fragmentation of liquid helium droplets doped with xenon , 2000 .

[34]  J. Northby,et al.  Potential of an ionic impurity in a large 4He cluster , 1999, physics/9905009.

[35]  J. Seong,et al.  Short-time charge motion in Hen+ clusters , 1998 .

[36]  K. Janda,et al.  Capture and ionization of argon within liquid helium droplets , 1998 .

[37]  K. Janda,et al.  The resonant charge hopping rate in positively charged helium clusters , 1998 .

[38]  V. Kresin,et al.  Capture of lithium by 4He clusters: Surface adsorption, Penning ionization, and formation of HeLi+ , 1997 .

[39]  T. Möller,et al.  Discrete Visible Luminescence of Helium Atoms and Molecules Desorbing from Helium Clusters: The Role of Electronic, Vibrational, and Rotational Energy Transfer. , 1997 .

[40]  V. A. Apkarian,et al.  CHARGE TRANSFER WITHIN HE CLUSTERS , 1996 .

[41]  J. Toennies,et al.  The photoionization of large pure and doped helium droplets , 1996 .

[42]  M. W. Cole,et al.  The binding of alkali atoms to the surfaces of liquid helium and hydrogen , 1995 .

[43]  Möller,et al.  Electronic excitations in liquid helium: The evolution from small clusters to large droplets. , 1993, Physical review letters.

[44]  J. Toennies,et al.  Anomalies in the reactions of helium(1+) with sulfur hexafluoride embedded in large helium-4 clusters , 1993 .

[45]  J. Northby,et al.  Excitation and ionization of 4He clusters by electrons , 1991 .

[46]  Nascimento,et al.  Photoionization cross sections and dynamic polarizabilities for the lithium atom and positive ion using L2 basis sets and correlated wave functions. , 1990, Physical review. A, Atomic, molecular, and optical physics.

[47]  Toennies,et al.  Capture of neon atoms by 4He clusters. , 1990, Physical review letters.

[48]  A. Stace,et al.  The fragmentation of molecular ions in association with large inert gas clusters , 1988 .