Belfast, July 1, 2003 A3: DESIREE (Double ElectroStatic Ion Ring ExpEriment) Designand examples of planned experiments Henning Schmidt, Stockholm University
Stockholm Low-Energy facilities: • DESIREEDouble ElectroStatic Ion Ring ExpEriment. • CRYSIS (EBIS source for very high charge states e.g. U70+) • ECR ion source for intense beams of moderately high charge states.
Outline • The DESIREE project • Motivation: Mutual Neutralization • Brief technical description • Planned experiments • AMO Physics • Example: Diffuse interstellar absorption bands • Biomolecules • Example: ‘Electron Capture Dissociation’ • Summary
Plasma environments: • The degree of ionization is a determining factor for the ongoing chemistry. Processes that affect this parameter are therefore crucial. • Electron-Ion recombination: • X+ + e- X + h (atomic recombination)AB+ + e- A + B (dissociative recombination) • Mutual Neutralization : • X+ + Y- X + YA- + BC+ A + BC or A + B + C
DESIREE Ion sources: Plasma Ion Sources Sputter Source (Negative Ions) ESI Source (Biomolecules) ECRIS (Highly Charged Ions) Double Electro-Static Ion Ring ExpEriment • Double-walled vacuum vessel • Outer tank 300K - Inner tank 15K • Cooling by cryogenerators • Expected vacuum in inner part • 300 K: <10-11 mbar • 15 K: Density reduced by order(s) of magnitude 1 m
Position-sensitive detector ELISA 1 m DESIREE
Count Rate estimates: Merged-beams experiments • Longitudinally: Kinematical compression • Transversely: Ion optics determines: < 1 eV seems feasible. • Can beam cooling be developed? • Example: MN H-+H2+E=10 keV/amu, Erel=1 eV, Amax=1 cm2,=1.6.10-14cm2 (COB), I+=I-=100 nA, L=80 cm: 44 s-1 • Background rate is similar - The key point is that in MN there are (at least) two neutrals in coincidence!! • How about experiments with Biomolecules? RN: In above example N=4.106. Feasible for ESI with trap Relative velocity definition:
Three special features of DESIREE: • Double-ring structure: • Merged beams positive/negative ion collisions. • Cryogenic system: • Extremely good vacuum Long storage lifetime. • Internally cold molecular ions. • Electrostatic confinement: • High mass-to-charge ratios (i.e. Biomolecules). • Absence of magnetic-field mixing in lifetime measurements
Examples of proposed experiments at the DESIREE facility: • Atoms and ‘Small’ Molecules: • Single-Ring Experiments • Lifetime measurements of metastable ions (He-, C60q+,…) • LASER spectroscopy of atomic/molecular ions (e.g. Cn-) • Merged-Beams Experiments • Mutual Neutralization Collisions • Fundamental systems (e.g. H-+H2+ …..) • Astrophysical plasmas (e.g. Cn-+H3+, H3O+,….) • Atmospherical ion chemistry. • Collisions involving fullerenes(C60q++C60-, Ar8++C60-,….)
Examples of proposed experiments at the DESIREE facility: • Biomolecules: • Biomolecules: • Single-Ring Experiments (already pursued at ELISA) • Lifetime and stability(J.U.Andersen et al, to be published) • LASER spectroscopy(e.g. GFP: S.B.Nielsen et al PRL 87, 228102 (2001)) • Biomolecules: • Single-Ring Experiments (already pursued at ELISA) • Lifetime and stability(J.U.Andersen et al, to be published) • LASER spectroscopy(e.g. GFP: S.B.Nielsen et al PRL 87, 228102 (2001)) • Merged-Beams Experiments • Electron Capture Dissociation in Negative/Positive ion collisions • Coulombic explosions induced by highly charged ions
Electron Capture Dissociation • ECD is important in protein sequencing because it breaks other bonds than those accessed in collision-induced dissociation. • ECD is studied by introducing electrons in the plasma of FT-ICR mass spectrometer. No control of electron impact energy. • Using simple negative ion to carry the electron, low (even below zero) and well-controlled relative energy is obtained.
Electron-transfer 10 a0 10 a0
Area of impact for ’distant’ collisions. • Experimental indication of distant collision: • Detection of neutral at proper time in relation to the arrival of the biomolecule(ar fragments)
Summary: • DESIREE can be built! • We can do new AMO physics in single-ring and particularly in merged-beams configuration (Mutual Neutralization) • Spectroscopy and lifetime measurements for biomolecular ions - ELISA • ’ECD’ like processes and HCI-biomolecular ion interaction in merged-beams - DESIREE unique The End!
DESIREE People: New Life! New Leif? • Primary investigator: Ö. Skeppstedt • Design group:K-G Rensfelt, M. Andersson, L. Bagge,H. Danared, J. Jensen, L. Liljeby, H.T. Schmidt, K. Schmidt, A. Simonsson • Contributors to the Scientific Programme:H. T. Schmidt, H. Cederquist, T. Hansson,J. Jensen, M. Larsson, S. Mannervik,P. vd Meulen, J. Pettersson. P. Royen,E. Uggerud, R. A. Zubarev