Showing papers by "Goran Pichler published in 2000"
TL;DR: In this paper, the authors present absorption and photoluminescence features of four samples of carbazole molecules substituted with various electronacceptor groups, and show that depending on the strength of the donor-acceptor internal charge transfer, both the absorption and emission spectra are more or less redshifted.
Abstract: We present absorption and photoluminescence features of four samples of carbazole molecules substituted with various electron–acceptor groups. These molecules named 1-(N-ethylcarbazolyl)-2-substituted-2-cyanovinylene contain in their structure the electron–donor carbazole nucleus and cyanovinylene bearing either another nitrile function, an ethylester, a phenyl, or a para-nitrophenyl groups. It is shown that depending on the strength of the donor–acceptor internal charge transfer, both the absorption and emission spectra are more or less redshifted. It is found that the ethyl-ester derivative displays the best relative photoluminescence efficiency among all the samples and its peak is measured at 490 nm when taking amorphous thin film. The microcrystalline powder form of the same material exhibits spectral narrowing and shift of the peak emission. We obtain further narrowing of the emission band and further redshifting of the emission when we illuminate, transversely, a glass capillary containing the crystalline sample by an ultraviolet light-emitting diode.
25 citations
TL;DR: In this paper, the self-breakdown voltage and the breakdown voltage for laser initiation of discharge were compared for different number densities of lithium vapor, and conditions for laser ignition of the discharge were described.
Abstract: Ignition of lithium glow discharge below self-breakdown voltage is studied for three cases of laser excitation of lithium vapor: the quasiresonant line at 460.3 nm $(2\stackrel{\ensuremath{\rightarrow}}{p}4d),$ the two-photon resonant line at 639.1 nm $(2\stackrel{\ensuremath{\rightarrow}}{s}3d$ transition), or the first resonance at 670.8 nm $(2\stackrel{\ensuremath{\rightarrow}}{s}2p$ transition). The conditions for laser ignition of the discharge are described. The differences between the self-breakdown voltage and the breakdown voltage for laser initiation of the discharge are given for different lithium number densities.
8 citations
TL;DR: In this article, the authors used two-photon excitation of the lithium 3d atomic level in a lithium-cadmium vapor mixture to observe cadmium atomic transitions and the LiCd blue-green excimer band.
5 citations
TL;DR: In this article, the authors investigated the emission spectrum of LiH molecules from an electric discharge in a heat-pipe oven, and they found that one part of the LH molecules formed in the discharge is created in chemical quenching of excited lithium atoms by H2.
Abstract: We investigated emission spectrum of LiH molecules from an electric discharge in a heat-pipe oven. The optimal conditions for the most intense LiH emission regarding the vapour pressures of helium, hydrogen and lithium were found to be 2.5 Torr, 8.5 Torr and 0.9 mTorr, respectively. The important role of helium gas in increasing the LiH emission intensity is described. The number density of the lithium atoms in the first excited state, Li(2p) and the LiH emission, was measured for different hydrogen pressures and currents through the discharge. We found that one part of the LiH molecules formed in the discharge is created in chemical quenching of excited lithium atoms by H2 . We performed the theoretical simulations for observed LiH A 1 + -X 1 + emission band. The rotational temperature and the population distribution of vibrational levels in the LiH A 1 + state were determined. We also describe the search for emission from the LiH C 1 + electronic state in the spectrum, which at present is unsuccessful.
4 citations
TL;DR: In this paper, quasiresonant laser excitation of Li-Cd vapor mixtures at 460.3 nm and 497.2 nm (2p-4s) was performed.
Abstract: We performed quasiresonant laser excitation of Li–Cd vapor mixtures at 460.3 nm (2p–4d) and 497.2 nm (2p–4s). The initial population of the Li(2p) level is caused by three processes: collisional dissociation or photodissociation of the Li2(B1Πu) molecules or energy transfer in Li2(B1Πu) and Li(2s) collisions. The Li(4d,4s) atoms radiatively decay towards Li(3p), from which collisional population transfer to Cd(53PJ) occurs, followed by three-body reactive collisions which produce the LiCd(22Π ) excimer states
1 citations