International Journal of Mass Spectrometry 303 (2011) 27–30 Contents lists available at ScienceDirect International Journal of Mass Spectrometry journal homepage: www.elsevier.com/locate/ijms First investigation of phase-shifted Ramsey excitation in Penning trap mass spectrometry M. Eibach a,b,∗ , T. Beyer b,c , K. Blaum c , M. Block d , K. Eberhardt a , F. Herfurth d , J. Ketelaer c,e , Sz. Nagy c,d , D. Neidherr c,d , W. Nörtershäuser a,d , C. Smorra a,b a Institut für Kernchemie, Johannes Gutenberg-Universität Mainz, Fritz-Straßmann-Weg 2, 55128 Mainz, Germany b Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Philosophenweg 12, 69120 Heidelberg, Germany c Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany d GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstraße1, 64291 Darmstadt, Germany e Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudinger Weg 7, 55128 Mainz, Germany article info Article history: Received 15 November 2010 Received in revised form 7 December 2010 Accepted 8 December 2010 Available online 16 December 2010 PACS: 07.75.+h 21.10.Dr 82.80.Qx Keywords: Mass spectrometry Penning trap Ramsey excitation abstract The excitation with time-separated oscillatory fields of the ion’s cyclotron motion inside a Penning trap is used to improve the precision of mass measurements. In this work at TRIGA-TRAP the effect of a phase shift of the radio frequency field between the two Ramsey excitation pulses on the resulting ion- cyclotron-resonance time-of-flight line shape is investigated and compared with theoretical predictions. © 2010 Elsevier B.V. All rights reserved. 1. Introduction The mass and its direct connection to the binding energy reflects all forces between the nuclear constituents. Therefore, a precise knowledge of the mass is required in many physical applications with accuracies ranging from ım/m = 10 -5 down to ım/m = 10 -12 [1,2]. Penning trap mass spectrometers like TRIGA-TRAP [3] achieve high precision by converting the mass measurement into a fre- quency measurement of an ion’s cyclotron frequency  c = qB/(2m) with charge-to-mass ratio q/m, which is stored in the superposition of a strong homogeneous magnetic field B and a weak electrostatic quadrupole field V [4].  c is in this case determined by the excitation of the ion’s radial eigenmotions and the measurement of its time- of-flight to a detector outside the magnetic field [5]. The so-called time-of-flight ion-cyclotron-resonance (TOF-ICR) [6] is obtained by measuring the ion’s time of flight as a function of the excitation ∗ Corresponding author at: Institut für Kernchemie, Johannes Gutenberg- Universität Mainz, Fritz-Straßmann-Weg 2, 55128 Mainz, Germany. E-mail address: martin.eibach@uni-mainz.de (M. Eibach). frequency which is scanned around  c . The shape of the resonance curve depends greatly on time structure and phase between the excitation pulses. Thus, the influence of these parameters has to be examined systematically to optimize precision and to cancel out certain systematic errors. In 1989, Ramsey received the Nobel Prize for the invention of the separated oscillatory fields method [7], which was used in Penning traps for the first time in 1992 for the excitation of the cyclotron motion [8,9]. Later on, the theoretical line shape of the corresponding TOF-ICR resonance was derived [10] and tested experimentally at different facilities with mass measurements of short-lived nuclides including a demonstration of an additional significant gain in precision compared to a continuous excitation, see, e.g. [11–14]. The effect of phase shifts in the oscillatory fields on molecular beams was already discussed by Ramsey in 1951 [15]. Experimental studies of the effect on ions in Penning traps and on the measured TOF-ICR line-shape which is theoretically addressed in [10] have not been performed yet. In this report, the results of experimental tests of the theory concerning phase shifts between the two rf pulses used to excite ions in a Penning trap are presented. 1387-3806/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.ijms.2010.12.006