Realisierung neuer Laserkühlverfahren und Spektroskopielaser für einen optischen Magnesium-Frequenzstandard

[no abstract

Absolute frequency measurement of the magnesium intercombination transition 1S0→3P1^1S_0 \to ^3P_1

We report on a frequency measurement of the $(3s^2)^1S_0\to(3s3p)^3P_1$ clock transition of $^{24}$Mg on a thermal atomic beam. The intercombination transition has been referenced to a portable primary Cs frequency standard with the help of a femtosecond fiber laser frequency comb. The achieved uncertainty is $2.5\times10^{-12}$ which corresponds to an increase in accuracy of six orders of magnitude compared to previous results. The measured frequency value permits the calculation of several other optical transitions from $^1S_0$ to the $^3P_J$-level system for $^{24}$Mg, $^{25}$Mg and $^{26}$Mg. We describe in detail the components of our optical frequency standard like the stabilized spectroscopy laser, the atomic beam apparatus used for Ramsey-Bord\'e interferometry and the frequency comb generator and discuss the uncertainty contributions to our measurement including the first and second order Doppler effect. An upper limit of $3\times10^{-13}$ in one second for the short term instability of our optical frequency standard was determined by comparison with a GPS disciplined quartz oscillator.Comment: 8 pages, 8 figure

Experimental and Computational Evidence of non-MEP Pathways in the Fragmentation and Rearrangement of Bicyclo[3.3.1] heptane Diazonium Ions

The non-minimum energy pathways on the fragmentation of bicyclic diazoniumions and subsequent carbocationic rearrangements has been studied by a combination of computational chemistry (MD simulations, IRC, stationary point analysis) and experiments (TR-IR and UV from ps to µs, NMR kinetics).</div

Frequency-stabilized Nd:YVO4 thin-disk laser

We have developed a Nd:YVO4 thin-disk laser at 914 nm with single-frequency operation and active frequency stabilization to a low-finesse reference cavity. The spectral density of laser frequency noise is analysed by means of noise measurements at the error point of the frequency control loop. To address the 31S0&#8594;33P1 magnesium intercombination line at 457 nm, we use an external frequency doubling stage based on periodically poled KTiOPO4 for the generation of more than 150-mW output power at 457 nm. Optical beat signal measurements at 457 nm with a frequency-stable dye laser show a short-time line width of the thin-disk laser of less than 100 kHz