Department Highly Sensitive X-ray Spectroscopy

Cryogenic Ion Trap

X-ray spectroscopy and XMCD of trapped molecular, cluster, and atomic ions

Ion Trap Setup

Experimental Setup

An overview of the experimental setup is shown on the left side. The apparatus can be roughly divided into four segments: cluster source, mass filter, ion trap, and time-of-flight (ToF) mass spectrometer. Each segment is housed in a differential pumping stage with the pressure decreasing from around 1mbar in the source chamber to about 10^-9 mbar in the spectrometer chamber. The transmission of the ions between stages is achieved by linear multipole radio frequency (RF) ion guides and/or electrostatic ion lenses.

XMCD of Metal Clusters in the Gas Phase

By applying x-ray magnetic circular dichroism spectroscopy on mass-selected cluster ions in an ion trap, we can investigate the cluster size-dependence of their magnetic properties. While in the ion trap, the ions are cooled down to temperatures as low as 8K and magnetized by the magnetic field of up to 5T generated by the solenoid.

Recent Publication: Large orbital magnetic moments of small, free cobalt cluster ions Co_n⁺ with n ≤ 9 https://doi.org/10.1088/1361-648X/aae54a

NEXAFS of Molecular Ions

Using an electrospray ion source together with the radio-frequency ion funnel shown on the left, we can bring coordination compounds from solution into the gas-phase for their solvent-free investigation with near-edge x-ray absorption fine structure spectroscopy.

Research Highlights

S. C. Meier, A. Holz, J. Kulenkampff, A. Schmidt, D. Kratzert, D. Himmel, D. Schmitz, E.-W. Scheidt, W. Scherer, C. Bülow, M. Timm, R. Lindblad, S. T. Akin, V. Zamudio-Bayer, B. von Issendorff, M. A. Duncan, J. T. Lau, I. Krossing, Access to the bis‐benzene cobalt(I) sandwich cation and its derivatives: synthons for a "naked" cobalt(I) source?, Angew. Chem. Int. Ed. 57, 9310 (2018)

V. Zamudio-Bayer, K. Hirsch, A. Langenberg, M. Niemeyer, Marlene Vogel, A. Ławicki, A. Terasaki, J. T. Lau, B. von Issendorff, Maximum spin polarization in chromium dimer cations as demonstrated by x-ray magnetic circular dichroism spectroscopy, Angew. Chem. Int. Ed. 54, 4498 (2015)

K. Hirsch, V. Zamudio-Bayer, A. Langenberg, M. Niemeyer, B. Langbehn, T. Möller, A. Terasaki, B. v. Issendorff, J. T. Lau, Magnetic moments of chromium-doped gold clusters: The Anderson impurity model in finite systems, Phys. Rev. Lett. 114, 087202 (2015)

M. Niemeyer, K. Hirsch, V. Zamudio-Bayer, A. Langenberg, M. Vogel, M. Kossick, C. Ebrecht, K. Egashira, A. Terasaki, T. Möller, B. v. Issendorff, J. T. Lau, Spin coupling and orbital angular momentum quenching in free iron clusters, Phys. Rev. Lett. 108, 057201 (2012)

J. T. Lau, J. Rittmann, V. Zamudio-Bayer, M. Vogel, K. Hirsch, Ph. Klar, F. Lofink, T. Möller, B. von Issendorff, Size dependence of L_2,3 branching ratio and 2p core hole screening in x-ray absorption of metal clusters, Phys. Rev. Lett. 101, 153401 (2008)

Cryogenic Ion Trap

X-ray spectroscopy and XMCD of trapped molecular, cluster, and atomic ions

Experimental Setup

XMCD of Metal Clusters in the Gas Phase

NEXAFS of Molecular Ions

The HZB in brief

Training and Vacancies