The sensitivity of molecular fingerprinting is dramatically improved when the absorbing
sample is placed in a high-finesse optical cavity, because the effective path length is
increased. When the equidistant lines from a laser frequency comb are simultaneously …

We have measured the 1 S–2 S transition frequency in atomic hydrogen via two-photon
spectroscopy on a 5.8 K atomic beam. We obtain f 1 S–2 S= 2 466 061 413 187 035 (10) Hz
for the hyperfine centroid, in agreement with, but 3.3 times better than the previous result [M …

Advances in optical spectroscopy and microscopy have had a profound impact throughout
the physical, chemical and biological sciences. One example is coherent Raman
spectroscopy, a versatile technique interrogating vibrational transitions in molecules. It offers …

The mid-infrared part of the electromagnetic spectrum is the so-called molecular fingerprint
region because gases have tell-tale absorption features associated with molecular
rovibrations. This region can be for instance exploited to detect small traces of …

A passive optical resonator is used to enhance the power of a pulsed 78MHz repetition rate
Yb laser providing 200fs pulses. We find limitations relating to the achievable time-averaged
and peak power, which we distinguish by varying the duration of the input pulses. An …

We apply a recently demonstrated method for precision spectroscopy on strong transitions in
trapped ions to measure both fine-structure components of the 3 s− 3 p transition in M 24 g+
and M 26 g+. We deduce absolute frequency reference data for transition frequencies …

We report on the first (to our knowledge) demonstration of nonlinear dual-frequency-comb
spectroscopy. In multi-heterodyne femtosecond Raman-induced Kerr-effect spectroscopy,
the Raman gain resulting from the coherent excitation of molecular vibrations by a spectrally …

Electronic wavepackets composed of multiple bound excited states of atomic neon lying
between 19.6 and 21.5 eV are launched using an isolated attosecond pulse. Individual
quantum beats of the wavepacket are detected by perturbing the induced polarization of the …

The decay of highly excited states of xenon after absorption of extreme ultraviolet light is
directly tracked via attosecond transient absorption spectroscopy using a time-delayed near-
infrared perturbing pulse. The lifetimes of the autoionizing 5 s 5 p 6 6 p and 5 s 5 p 6 7 p …

We demonstrate sub-Doppler laser spectroscopy with a beam of L 7 i+ ions stored at 33.8%
of the speed of light in the experimental storage ring at GSI. Using two lasers, the one
copropagating and the other counterpropagating, with respect to the ion beam, a …