JRA3: Cold and Complex (Biomolecular) Targets

JRA3: Cold and Complex (Biomolecular) Targets Co-ordinators: Thomas Schlathölter and Reinhard Morgenstern • Why study interaction of HCI with biomolecular targets? • Basic physics: large energy transfer in a single collision! • Applied physics: HCI as secondary products, e.g. in radiation therapy • Why “cold” targets? • All molecules in one electronic (ground-) state • Possibility of recoil momentum spectroscopy

Tasks and Volunteers A. Solid biomolecular targets,CEA/Caen (Huber, Lebius) B. Ionic biomolecular targets NUI/Maynoth (O’Neill, v.d. Burgt) QUB/Belfast (Greenwood, Williams, McCullough, OUL/London (Mason), KVI/Groningen (Schlathölter, Morgenstern) C. Neutral gasphase biomolecular targets CUB/ Bratislava (Matejcik), OUL/London (Mason), UIBK/Innsbruck (Scheier, Märk), LCAR/Toulouse (Moretto Capelle) D. Ultracold neutral targets (nanodroplets, MOT’s) UBI/Bielefeld (Stienkemeier, Werner),OUL/London (Mason), KVI/Groningen (Schlathölter, Morgenstern) E. Datareduction and analysis UBI/Bielefeld (Werner),

A. Solid biomolecular targets In the case of a nucleic bases, a compressed powder is used as a 'solid' target, which can be bombarded with ions of different charges and energies, and at different incidence angles. Fragmentation spectra are analysed with mass-spectrometric methods. DeOxyAdenosine

(m=241) Dependence of the fragmentation of thymidine on the incidence angle inset part magnified by a factor 10 Huber et al, Caen

Pulsed ion beam QUB arrangement to study neutral targets Laser B. Ionic biomolecular targets Adaption of MALDI techniques Desorption laser Desorption of ions and neutrals

laser pulse trapping and cooling of desorbed ions expanding plume (neutrals and ions) bio molecules matrix MALDI sample (located in a trap endcap) the principle to get an ionic target 3rd or 4th harmonic of our Nd:YAG-laser (355 or 266 nm) Quantel Brilliant pulse length: ~5 ns frequency: 50 Hz fluence: up to 200 mJ/cm2 @ 1064 nm. MALDI and an electrostatic trap

ions YAG laser TOF analysis by means of a FAST P7888 TDC (1ns resolution, 1ns deadtime, 1 GHz) Several events per sweep: possibility of coincidence experiments electrostatic analyzer trapped ions as target for HCI/fs-laser pulses ECRIS or fs-laser detector reflectron MALDI sample fields are switched off for MCI bunch passage! trap Einzel lens

ions are accumulated and cooled • the trapping potentials are switched of • a pulse of MCI passes the trapping region through the ring electrode 5) a dc pulse applied to the second end cap extracts molecular ions and fragments 1) 2,3) 4) 5) measurement cycle 1) laser desorbed ionic biomolecules are introduced from one electrode of the trap • ions pass a reflectron TOF spectrometer reflectron trap/TOF tandem leads to high mass resolution which can be extended to high m/q values allowing for the study of large biomolecules.

C. Neutral gasphase bio-molecular targets Target production via evaporation possible for DNA or RNA building bloks like thymine or uracil Problem: Are the molecules in their electronic groundstate? Approach for a solution: Check via reactions which are sensitive for electronic state Example: H-loss or fragmentation in low energy attachment reactions

Uracil Glycine Thymine P. Scheier, T. Märk Electron attachment (Scheier, Märk) M + e‾ → (M-H)‾ + H (×0.33) 4 3 Cross section (10-20 m2) 2 1 0 0 1 2 3 4 Electron energy (eV)

D. Production and manipulation of ultracold targets • Capture in magneto-optical traps (MOT’s) • sympathetic cooling of molecules in a MOT • Capture of biomolecules in He nano droplets

Load from background vapor • 106 –107 Sodium atoms • sub mm size cloud • 200-300 mK (<30 neV!) laser light + magnetic quadrupole field = MOT Ultra cold Na target in a Magneto Optical Trap (MOT) near resonance laser light to trap and cool Na atoms:

Na4+ Na3+ Na2+ 110 110 110 100 100 100 90 90 90 80 80 80 70 70 70 60 60 60 transversal momentum transversal momentum transversal momentum 50 50 50 40 40 40 30 30 30 20 20 20 10 10 10 0 0 0 -12 -10 -8 -6 -4 -2 0 2 4 -12 -10 -8 -6 -4 -2 0 2 4 -12 -10 -8 -6 -4 -2 0 2 4 longitudinal momentum longitudinal momentum longitudinal momentum TOF and recoilspectroscopy of O6+ + Na collisions

Apparatus for He nanodroplet studiesToennies et al , Physics Today, Feb. 2001, 31-37

Helium droplet beam machine Fakultät für Physik

Formation of large molecular complexes in helium droplets Formation of large molecular complexes in helium droplets Spectroscopy of excitonic transitions in PTCDA nanostructures at 380 mK M. Wewer and F. Stienkemeier, Phys. Rev. A 37, 2002

Laser induced fluorescence spectrum of PTCDA (a) in a nanodroplet (b) in the gasphase F. Stienkemeier and A.F. VilesovJ.Chem. Phys.115 (2001) 10119

E. Data reduction and analysis A non-trivial task! High-dimensional parameter space! (up to 30-40 parameters per collision event) Pattern recognition Fitting procedures based on e.g. maximum entropy methods

Fragmentation of thymidine by ions with high and low charge Xe20+, 400 keV O2+, 40 keV Huber et al, Caen NIM B 205 (2003) 666–670

JRA3: Cold and Complex (Biomolecular) Targets