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A new ethanol vapor detection probe based on an optical fiber long period grating overlaid with a zinc oxide (ZnO) nanorods layer is presented. The ZnO nanorod layer was developed onto the cladding of the fiber using aqueous chemical growth, seeded by a thin layer of metallic Zn. The growth of the ZnO nanorods overlayer onto the long period grating cladding is monitored in real time for investigating its effect on the spectral properties of the device and its subsequent role in the sensing mechanism. Results are presented, on the correlation between the growth time of the ZnO layer and the ethanol vapor detection performance. Reversible spectral changes of the notch extinction ratio of more than 4 dB were recorded for ~50 Torr of ethanol vapor concentration. In addition, photoluminescence emission studies of the ZnO overlayer performed simultaneously with the optical fiber spectral measurements, revealed significant ethanol induced changes in the intensity of the bandgap peak.

The resonance enhanced multiphoton ionization (REMPI) spectrum of jet-cooled CS2 has been recorded in the one-photon wavelength range 460–500 nm, corresponding to the three photon excitation energy range 60 000–65 000 cm−1. A previous assignment of one photon forbidden transitions in this region to 3d Rydberg states is shown to be incorrect and reassigned to the 4pπ 1,3Δu states. In fact all the observed states in this region can be assigned to 4p Rydberg states; the 4pσ 1,3Πu states at 62 768 and 62 083 cm−1, respectively, and the 4pπ 1,3Δu states at 64 214 and 63 698 cm−1, respectively. Another band at 64 374 cm−1 may be due to a three photon excitation to the 4pπ 1Σ+u Rydberg state. Our resolution is sufficient to resolve band shapes enabling symmetry assignments when coupled with their polarization behavior. The fact that the origin bands are not degraded and that Δν=0 sequence bands are strongly excited whereas Δν≠0 transitions are either absent or very weak implies that the upper states have a linear geometry similar to that of the ground state. A comparison of singlet–triplet splittings suggests the 4pπ Δu states have stronger Hund’s case (c) character than the 4pσ Πu state. While CS+2 was generally the predominant ion formed, resonance ionization through the 1Δu←X 1Σ+g origin band led to an unusual predominance of S+ and CS+ ions. This is explained by multiphoton fragmentation of CS+2 via an accidental one-photon resonance from the X 2Π1/2 (v=0) ionic ground state.