These data show the first time that any structure has ever been observed at this transition for negative sulfur ions or any isoelectronic species. The Zeeman transitions found in this investigation are in fairly good agreement with the theoretical values. These data also represent the first time that individual Zeeman transitions have been observed at a 1.0-T magnetic field. Photodetachment from the negative sulfur ion in a magnetic field is a well studied phenomenon at the 2 P 3/2 → 3 P 2 transition, known as the electron affinity. It is modeled using the Blumberg, Itano, Larson (BIL) Theory. The goal of this work is to apply the BIL theory’s prediction to the less studied 2 P 1/2 → 3 P 2 transition. A Penning ion trap was used to trap the ions and photodetachment was achieved using a continuous wave tunable dye laser. For the first time, structure due to the magnetic field in the detachment cross-section was observed at this transition. 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Wells, Davidson College, Davidson, North Carolina Abstract Active Layer References Background Apparatus Results The ions are held in a Penning ion trap in an ultra high vacuum (UHV) ~10 -8 Torr. A continuous-wave ring dye laser, with kiton red dye as a lasing medium, is used to provide photons for photodetachment. Light with π polarization was used in this investigation. The fraction of ions surviving detachment can be measured by using a radio frequency (RF) potential to cause the ion ensemble to oscillate in the trap. This generates a current which can be measure and compared to the pre-detachment current magnitude to find the fraction surviving. A photodiode allows the same amount of light of to be used for each run The negative sulfur ion has 2 bound states: 2 P 3/2 and 2 P 1/2 The ground state of the neutral sulfur atom is part of an inverted triplet: 3 P 2 (lowest state), 3 P 1, 3 P 0. In the absence of a magnetic field, the energy levels which make up the 2 P 1/2 and 3 P 2 states are degenerate. In the presence of an external magnetic field the 2 P 1/2 and 3 P 2 states split into 4 and 5 levels respectively. Instead of a single transition there are several transitions between these states. Which transitions are allowed is determined by conservation of momentum. Zeeman Effect A plot showing the fraction of ions surviving detachment as a function of photon energy. Notice that the fraction of ions surviving does not simply decrease with photon energy as it would in the absence of a magnetic field. Instead there is structure caused by a combination of the Zeeman transitions and the quantized orbits of the freed electron. The black arrows show the locations of the Zeeman transitions suggested by the data. The table below compares the Zeeman transitions measured in the experiment to the theoretical values. Thanks to Dr. John Yukich and the Davidson Physics Department Conclusions PolarizationInitial Z Component of Angular Momentum of Ion Final Z Component of Angular Momentum of Neutral Atom Initial Z Component of Angular Momentum of Electron Shift for n=0 cyclotron state (cm -1 ) π½1- ½0.545 π½0½0.778 π- ½ π- ½½0.389 σ½2- ½1.245 σ½1½1.479 σ½0- ½ σ½½0.078 σ- ½ σ- ½0½1.090 σ- ½- ½ σ- ½-2½ TransitionExperimental Frequency (cm-1) SpacingTheoretical Frequency (cm-1) SpacingExperimental- Theoretical Frequency (cm-1) TransitionExperimental Frequency (cm -1 ) SpacingTheoretical Frequency (cm-1) SpacingExperimental-Theoretical Frequency (cm-1) This plot shows another data set which covers a much larger range of photon energies. It shows evidence of 8 Zeeman transitions, which are compared to theoretical values in the table below.