Gerade/ungerade symmetry- breaking in HD at the n =2 dissociation limit
We report on a study of the I'1Πg outer well state of HD. Via a resonance-enhanced XUV + IR (extreme ultraviolet + infrared) excitation scheme, rovibronic levels (v = 0-2, J = 1-4) are populated and probed by pulsed lasers. Level energies are measured with an accuracy of 0.03 cm-1. Due to gerade-ungerade symmetry breaking, the long-range behavior of the I' potential in HD deviates from that of H2 and D2. When this deviation is taken into account a semi-empirical potential for the I'1Πg state may be constructed, resulting in better agreement with the observed level energies than derived from an adiabatic ab initio potential. With this new potential it is predicted that the I' well can sustain only 4 vibrational levels, with the v = 3 level having a binding energy of 1.38(3) cm-1. PACS Nos.: 33.80.Rv, 34.20.Cf, 33.20.Ni, 31.50.+w
Observation of g/u-symmetry mixing in the high-n Rydberg states of HD.
The structure and dynamics of high-n Rydberg states belonging to series converging to the (v(+) = 0, N(+) = 0-2) levels of the X(+) (2)Σ(g)(+)electronic ground state of HD(+) were studied by high-resolution spectroscopy from the GK (1)Σ(g)(+) (v = 1, N = 1) state under field-free conditions. Three effects of g/u-symmetry breaking were detected: (i) Single-photon transitions from the GK (v = 1, N = 1) state of gerade symmetry to the 30d21 and 31g22 Rydberg states of gerade symmetry were observed after careful compensation of the stray electric fields. (ii) The singlet 61p12 Rydberg state of ungerade symmetry was found to autoionize to the N(+) = 0, ℓ = 2 ionization continuum of gerade symmetry with a lifetime of 77(10) ns. (iii) Shifts of up to 20 MHz induced by g/u-symmetry mixing were measured for members of the np11 Rydberg series which lie close to nd21 Rydberg states. These observations were analyzed in the framework of multichannel quantum-defect theory. From the observed level shifts, the off-diagonal eigenquantum-defect element μ(pd) of singlet-π symmetry was determined to be 0.0023(3) and the corresponding autoionization dynamics could be characterized. The ionization energy of the GK (v = 1, N = 1) state of HD was determined to be 12 710.544 23(10) cm(-1).
The MR-TOF-MS isobar separator for the TITAN facility at TRIUMF
At TRIUMF’s Ion Trap for Atomic and Nuclear Science (TITAN) a multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) will extend TITAN’s capabilities and facilitate mass measurements and in-trap decay spectroscopy of exotic nuclei that so far have not been possible due to strong isobaric contamination. This MR-TOF-MS will also enable mass measurements of very short-lived nuclides (half-life > 1 ms) that are produced in very low quantities (a few detected ions overall). In order to allow the installation of an MR-TOF-MS in the restricted space on the platform, on which the TITAN facility is located, novel mass spectrometric methods have been developed. Transport, cooling and distribution of the ions inside the device is done using a buffer gas-filled RFQ-based ion beam switchyard. Mass selection is achieved using a dynamic retrapping technique after time-of-flight analysis in an electrostatic isochronous reflector system. Only due to the combination of these novel methods the realization of an MR-TOF-MS based isobar separator at TITAN has become possible. The device has been built, commissioned off-line and is currently under installation at TITAN.