Berlin 2005 – wissenschaftliches Programm
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A: Atomphysik
A 12: Precision Spectroscopy of Atoms and Molecules III
A 12.5: Fachvortrag
Dienstag, 8. März 2005, 11:45–12:00, HU 3075
Frequency metrology on the Mg 3s2→ 3s4p line at 202 nm for comparision with quasar data — •Sandro Hannemann, Eric-Jan van Duijn, Kjeld Eikema, and Wim Ubachs — Laser Centre, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
Possible cosmological variation of the fine structure constant α can be derived from comparision of spectra of quasars at high red-shift with laboratory spectra obtained in the modern epoch. For this purpose laboratory data at accuracies of <10−7 are required. Together with other lines found in quasar spectra, the Mg 3s2→ 3s4p transition at 202.5 nm has hitherto not been measured that precisely [1].
Here, a narrowband pulsed deep-UV laser based on an injection seeded gain switched Titanium:Sapphire (TiSa) oscillator is used for a LIF spectroscopy on a Mg atomic beam. The nearly Fourier limited output of the oscillator is enhanced in a bowtie TiSa amplifier and nonlinearly upconverted to the fourth harmonic. For absolute frequency calibration the cw seeding light at 810 nm is referenced to a femtosecond laser frequency comb.
[1] J.C. Berengut et al., arXiv:physics/0408017 v1 4 Aug 2004