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Laser spectroscopy is a powerful and versatile technique for the study of nuclear ground-state properties [1]. The precision with which these nuclear properties can be extracted from the isotopic shifts and hyperfine structure of optical transitions is defined by the observable spectral line width. The latter depends on different line broadening mechanisms existing due to the conditions of the experiment, as well as the laser line width. Lasers with extremely narrow width of emission light are often required for spectroscopic techniques used to study exotic nuclei [2] Pulsed Ti:Sapphire (Ti:Sa) lasers with ring-cavity design [3] and seeded by a continuous-wave (cw) single-mode laser are able to fulfill those requirements. However, the tunable range of the Ti:Sa lasing medium is limited to ~ 700-950 nm which can be extended to blue and UV wavelengths using common higher-harmonic generation techniques. Complementing this are dye lasers whose emission spectra, when pumped with 532-nm laser light, can cover the range of 540-900 nm and can also be extended to UV ranges in a similar fashion to Ti:Sa lasers but with higher power. Pulsed amplification of a cw single frequency dye laser in a dye cell pumped by a copper vapor laser has been demonstrated and successfully applied for resonance photoionization spectroscopy of radioisotopes in [4]. In this approach, the pulse length of pumping laser determines the spectral width of the amplified radiation according to the Heisenberg uncertainty principle. Preliminary studies performed with Nd:YAG laser pumping suggest that narrowband pulsed-dye amplification suffers from the existence of sidebands in the amplified light due to the amplitude modulation nature of the multimode pumping light. The characteristics of the system in terms of design, power and spectral width as well as the application to the in-gas-jet laser ionization and spectroscopy technique [5] will be discussed. Future applications for two-photon spectroscopy and electronic-affinity measurements will be presented.
[1] G. Neyens. Reports on Progress in Physics, 66:1251 (2003).
[2] Klaus Blaum, Jens Dilling, and Wilfried Nörtershäuser. Physica Scripta, T152 (2013).
[3] Volker Sonnenschein, PhD thesis, Jyväskylä (2015).
[4] V.I. Mishin et al., Ultrasensitive resonance laser photoionization spectroscopy of the radioisotope chain 157-172Tm produced by a proton accelerator, Sov. Phys. JETP 66, 235-242 (1987).
[5] R. Ferrer et. al. Nature Communications volume 8, 14520 (2017)
