Fluorescence excitation spectra of 4-(diisopropylamino)benzonitrile (DIABN) and 4-(dimethylamino)benzonitrile (DMABN) in thermal vapour and seeded jet expansions are compared. The spectrum of jet-cooled DIABN shows an intense 0±0-transition at 31751:8 cm À1 . The spectrum collapses at excess excitation energies above 800 cm À1 , indicating the presence of an ecient non-radiative decay channel. In the gas phase,¯uorescence emission of DIABN occurs from the intramolecular charge transfer (ICT) state. The non-radiative decay channel, therefore, is attributed to rapid ICT in the isolated molecule. The related compounds 4-(methylamino)-3,5-dimethylbenzonitrile (MHD), 4-(azetidinyl)-3,5dimethylbenzonitrile (M4D), and 4-(dimethylamino)-3,5-dimethylbenzonitrile (MMD) in the jet show extremely weak and structureless emission.

The S I state of jet-cooled 4-(N,N-dimethylamino)-4'-cyanostilbene (DCS) was studied by picosecond fluorescence spectroscopy. The line structure of the S O-* Sl-excitation spectrum is a superposition of transitions characteristic of isolated trans-sti~bene and the dimethylamino group. Rotational contour analysis and rotational coherence spectroscopy suggest a non-planar geometry of DCS in both electronic states. Fluorescence decays are monoexponential up to 3700 cm-I above the origin at 27038 cm-~. The lifetimes vary little up to 733 cm-~ ((¢) = 2.097 ns) and start to decrease above this energy because of the onset of photoisomerization. An RRKM-fit to the non-radiative rate coefficients yields a barrier height g o = 745 cm-I.

Passive remote sensing with a Fourier transform infrared (FTIR) spectrometer allows the detection and identification of pollutant clouds in the atmosphere. In this work, the measurement technique and a data analysis method that does not require a previously measured background spectrum are described. Recent experimental results obtained with a new high sensitive FTIR remote sensor are presented.Many situations do not allow the measurement of a background spectrum prior to the measurement of pollutants in order to perform background removal. After a radiometric calibration of the FTIR spectrometer with IR reference sources the spectral radiance of the environment can be measured. With the inverse function of Planck's radiation law, the (spectrally resolved) brightness temperature is computed. The temperature spectrum has a constant baseline for many natural materials that serve as the background in field measurements (forest etc.) because their emittance ε(ν) is high and almost constant in the spectral range 800-1200 cm -1. The influence of environmental and instrumental parameters on the sensitivity of the method is discussed. Experimental results are presented to illustrate the enhancement of the signal to noise ratio that can be achieved by the alignment of the spectrometer to backgrounds with a high temperature difference to the environment.

Interferometric Photo-Activation-Localization-Microscopy (iPALM) localizes single fluorescent molecules with 20 nm lateral and 10 nm axial resolution. We present a method utilizing glass coverslip lithography for correlative imaging between iPALM and scanning electron microscopy (SEM). Using iPALM on HIV Gag-Dendra virus-like particles (VLPs) we localized the position of HIV Gag proteins. Based on these localizations we reconstructed the central cavity of the VLPs along with imperfections within the HIV Gag lattice. The SEM images and iPALM images overlap and show imaging from single VLPs immobilized on glass coverslips. The localization of many HIV proteins including accessory proteins and Gag-Pol remains unknown, we discuss how the specificity of iPALM coupled with SEM has the potential for resolving more of HIV proteins.

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