Kyriaki Kosma

Learn More
A compact and robust scheme for broadband excitation of whispering gallery mode (WGM) resonances into a microsphere is demonstrated. A polymer microsphere (10 μm) is encapsulated into the capillary of a microstructured optical fiber, in direct contact with the guiding core. Such a configuration allows efficient and reproducible excitation of the(More)
We demonstrate that in a short Ar cell, generation of the fifth harmonic from 12 fs pulses at 810 nm directly results in ultrashort vacuum UV pulses at 162 nm. They have a spectral width of approximately 5 nm and a duration of 11+/-1 fs (1.4 times the transform limit), as measured by cross correlation with the fundamental pulses. Their energy (estimated to(More)
By focusing 805 nm pulses of low energy (0.2–1 mJ) into atmospheric-pressure argon, a supercontinuum is generated with a shortwavelength cutoff of 640, 250 and 210 nm for initial pulse durations of 45, 10 and 6 fs, respectively. It is shown numerically that the large shift of the UV cutoff and many features of the spectrum are caused by terms beyond the(More)
The third harmonic (270 nm, 11 fs), produced in a short argon cell from Ti-sapphire laser pulses (810 nm, 12 fs), was used to excite 1,3-cyclohexadiene to its lowest pipi* state (1B). Probing was done by transient ionization by the 810 nm pulses, measuring the yields of the parent and a fragment ion. As previously found with 10 times longer pulses, the(More)
Focusing 12 fs pulses of 800 nm with moderate energy (0.35 mJ) into atmospheric-pressure argon (Ar) gives rise to filamentation (self-focusing) and a supercontinuum with a very broad pedestal, extending to 250 nm. According to the present understanding, the short wavelengths are produced by self-phase modulation in the self-steepened trailing edge of the(More)
The fifth harmonic (162 nm, 11 fs), generated in a short argon cell from 12 fs Ti-sapphire laser pulses, was used to excite C2H4 and C2D4 in the maximum of the first pi pi* transition. Around 10% of the molecules were excited to the pi3s Rydberg state instead. The subsequent motion of the wave packet, moving over the potentials from the Franck-Condon region(More)
Here we report on a novel in-fiber microresonator coupler, which combines a microstructured optical fiber (MOF) and a polystyrene microsphere (PM), embedded into one of its empty capillaries. The MOF consists of a germanium-doped silica core (~2.5 m), suspended within three hollow channels with a maximum dimension of ~11 m. The microsphere has a diameter of(More)
On dissociation of M(CO)(6), M = Cr, Mo and W, by a femtosecond UV laser (<270 to 360 nm), pronounced coherent oscillations are observed in the pentacarbonyl products on probing by long-wavelength (810 nm) ionization in the gas phase. They are vibrations in the ground state, driven by the slope from a conical intersection on relaxation from the initially(More)
In the group-6 metal hexacarbonyls a number of metal-to-ligand charge-transfer (MLCT) and ligand-field (LF or d ! d) states can be excited in the near UV. The latter are repulsive. In equilibrium geometry, most of them are higher than the MLCT states. We probed the dynamics of photodissociation of M(CO)6 ! M(CO)5 + CO (M = Cr; some data also for M = Mo)(More)
  • 1