Goran Pichler

Electronic assignments of the violet bands of sodium

Abstract The puzzling violet bands of sodium ( ≈ 425-460 nm), known since 1932, are shown conclusively to arise from the superposition of two distinct continuum emission bands - one singlet (2 1 Σ + u → X 1 Σ + g ) and one triplet (primarily 2 3 Π g → 1 3 Π u + ). Each continuum emission system shows complex interference structure arising from multiple branches of the Mulliken difference potential.

The 458 nm diffuse band of the lithium dimer

Laser induced fluorescence studies of the lithium diffuse band at 458 nm were performed using single‐and double‐photon excitations. Single‐photon excitation was performed using UV lines of Ar++ and Kr++ lasers, and the diffuse band fluorescence was induced by collisions in 7Li2 and 6Li2. The double‐photon excitation process populated relevant upper states through several accidental coincidences for two‐step excitation in 7Li2. In two cases, in addition to structured continuum emission, an adjacent line spectrum was observed. In five other cases, two‐photon accidental coincidences produced collision induced fluorescence of the 7Li2 diffuse band. We also found (in a few cases) that the (two‐photon) excitation energy of the 2 3Πg state (with respect to the 1 3Σ+u state) was collisionally transferred to simultaneously excited lithium 2p atoms, thus creating a lithium atom in the 4d state.

Laser-induced chemiluminescence of the LiMg excimer

Abstract A UV Ar 2+ laser was used to excite specific levels in the C 1 Π u state of the 7 Li 2 dimer. A subsequent photochemical reaction with atomic Mg produced the LiMg excimer in excited C 2 Π and D 2 Σ + states. The observed bound-free excimer emission spectrum was compared with theoretical emission profiles based on potential energy curves and transition dipole moments obtained from ab initio calculation. These calculations also indicate avoided crossings between the A 2 Π and C 2 Π states, and B 2 Σ + and D 2 Σ + states of LiMg.

Blue Satellite Bands and Photoassociation Spectra of Ultracold Cesium

Atomic line self‐broadening was observed in ultracold cesium. Using resonant ionization detection we were able to photoassociate atoms into excited states of ultracold molecules below the second excited PJ atomic asymptotes Cs(6S1/2) + Cs(7P1/2) and Cs(6S1/2) + Cs(7P3/2). We were able to observe blue detuned satellite band features at 560 MHz and 800 MHz above the 7P1/2 and 7P3/2 atomic limits, respectively, as well as sharp hyperfine split features on the blue and red side of the atomic resonances. Such spectral features can be qualitatively supported by the local maxima in the long range molecular structure beyond 50 A.

Structured continua of the intermediate long-range Cs2 molecules

New development in cold collisions has revived the interest in the process of photoassociation, because the free-bound transitions are very selective at extremely low temperatures. Some molecular systems where photoassociation has been observed in the past may now be studied in much greater detail than ever before. The photoassociation from the weakly bound Cs2 molecules at elevated and ultra cold temperatures will form peculiar molecules in their excited states in the intermediate internuclear distances.

Near‐resonant femtosecond laser induced cone emission from rubidium vapor

In this work we report the CE from the dense rubidium vapor excited by the output from the mode-locked, 100 fs laser oscillator. The cone emission was observed only when the laser beam propagated through the high-density vapor (N>5x1016 cm− 3) and for the smaller densities no CE was observed. The laser central wavelength was changed in the wide interval, from the far blue wing of the D2 line to the far red wing of the D1 line. The observed CE in the far blue wing of the D2 line is interpreted as a consequence of the self-focusing and self-phase modulation according to the adiabatic following limit. The emission in the red wing of the D2 line shows defocusing of the propagating beam. In contrast to the CE reported so far, the bright central spot was not observed in the far blue wing. In the near blue wing the central spot appears due to the two- photon resonance at 778 nm. The temporal shape of the CE, measured by cross-correlation in the SHG crystal shows pulse breaking and extreme lengthening.