Direct observation of high-spin states in manganese dimer and trimer cations by x-ray magnetic circular dichroism spectroscopy in an ion trap

Abstract

The electronic structure and magnetic moments of free Mn2 (+) and Mn3 (+) are characterized by 2p x-ray absorption and x-ray magnetic circular dichroism spectroscopy in a cryogenic ion trap that is coupled to a synchrotron radiation beamline. Our results directly show that localized magnetic moments of 5 μB are created by 3d(5)((6)S) states at each ionic core, which are coupled ferromagnetically to form molecular high-spin states via indirect exchange that is mediated in both cases by a delocalized valence electron in a singly occupied 4s derived antibonding molecular orbital with an unpaired spin. This leads to total magnetic moments of 11 μB for Mn2 (+) and 16 μB for Mn3 (+), with no contribution of orbital angular momentum.

Electronic ground states of Fe2+ and Co2+ as determined by x-ray absorption and x-ray magnetic circular dichroism spectroscopy

“…The most intense product ion that results from 2p core excitation and relaxation is the atomic dication for both Fe For XMCD spectroscopy, the ion trap is placed inside the homogeneous magnetic field (µ 0 H = 5 T) of a superconducting solenoid. [35][36][37][38][39][40]44 Following the standard procedures, the XMCD spectrum is obtained as the difference of x-ray absorption spectra that are recorded with parallel and antiparallel orientation of the photon helicity relative to the direction of the applied magnetic field. The isotropic x-ray absorption spectrum is obtained by taking the average of the spectra of both photon helicities.…”

“…In particular for free as determined by gasphase x-ray magnetic circular dichroism (XMCD) spectroscopy [34][35][36][37][38][39][40] that was only recently introduced for free molecular ions. 39,40 All states that are found in our study carry significant orbital angular momentum that disagrees with theoretical preferences for Σ states.…”

Complex magnetic orders in small cobalt–benzene molecules

“…[8][9][10] More recently, X-ray magnetic circular dichroism spectroscopy (XMCD) has been used to determine independently the orbital-and spin-magnetic moments measured on a trapped and cooled gas of metal cluster ions. [11][12][13] Contrary to the SMMs, where the transition metal centers are surrounded by organic compounds and thus, protecting their magnetic moment, [14][15][16] the transition metal atoms in such organometallic clusters are in close proximity, leading to strong exchange interactions. Although these organometallic clusters made up of transition metal clusters and benzene rings share same magnetic properties with SMMs, their magnetism is much less studied.…”

The variable polarization undulator beamline UE52 PGM nanocluster trap at BESSY II

“…This is the main purpose of the beamline (Egorov et al, 2015;Langenberg et al, 2014;Niemeyer et al, 2012;Zamudio-Bayer, Hirsch, Langenberg, Kossick, et al, 2015;Zamudio-Bayer et al, n.d., 2013). In this respect, UE52 PGM nanocluster trap beamline is unique at BESSY II, because all other beamlines with elliptical polarization for exible use at BESSY II feature high divergence beam pro les with very short distances between the beamline exit port (last valve) due to the installed micrometer focus optics.…”