The wavelength of a femtosecond Ti:sapphire laser (TS, 800 nm) was converted into the ultraviolet (UV, 200 nm) using three β-barium borate crystals (β-BaB 2 O 4 ) for frequency doubling and subsequent mixing. The UV pulse was further converted into the vacuum ultraviolet (VUV, 185 nm) based on four-wave Raman mixing, in which a two-color pump beam consisting of the fundamental beam (800 nm) of the TS and the signal beam of an optical parametric amplifier (1200 nm) pumped by the TS was focused onto a capillary waveguide filled with hydrogen gas for molecular phase modulation and the single-color UV probe beam (200 nm) was then focused onto the waveguide for frequency modulation to generate anti-Stokes and high-order Stokes Raman sidebands at wavelengths of 185 and 218−267 nm, respectively. The efficiency of conversion from the UV (200 nm) to the VUV (185 nm) was 6%. The ionization energy was calculated for 13 amino polycyclic aromatic hydrocarbons using density functional theory, since they are associated with the development of occupational bladder cancers. The values calculated by the B3LYP/cc-pVDZ and ωB97Xd/cc-pVTZ methods were 6.24−7.14 eV (199−174 nm) and 6.41−7.35 eV (194−169 nm), respectively. A sample containing a mixture of 9-aminoanthracene, 3-aminofluoranthene, and 1-aminopyrene was separated by gas chromatography (GC), and the eluents were ionized with the VUV pulse (0.015 μJ) in mass spectrometry (MS). The analytes were observed on a two-dimensional display of GC/MS, and the detection limit obtained by single-photon ionization of 3-aminofluoranthene was 1 ng/μL.

A two-color femtosecond pump beam (800 and 1200 nm) and a one-color femtosecond probe beam (267 nm) were focused into a hydrogen gas to generate high-order Raman sidebands in the spectral region of 172-343 nm. The efficiency of frequency conversion to neighboring Stokes/anti-Stokes emission was 18%. Simultaneously, vacuum-ultraviolet stimulated emission was observed at 154.2 nm with the assistance of four-wave Raman mixing. This observation was explained as a Lyman transition (B 1 u + → X 1 g +) of the hydrogen.

Optical second-harmonic generation (SHG) in self-assembled ampholytic mega-molecule polysaccharide sacran is an interesting phenomenon but its origin has not been clarified. SHG-active sacran aggregates in dried cast films made from ultrasonicated 0.5 wt% sacran aqueous solutions were studied at microscale using the scanning electron microscope and the energy dispersive X-ray technology. Hexagonal morphology was observed frequently with the size of a few to tens of micrometers. The calcium density was higher in the area showing the SHG signals. In sum-frequency generation spectra of the SHG-active sacran aggregates, vibrational modes of functional groups such as CH3, CH 2 , and −COOH of the sacran molecules and OH of the water molecules were identified. The structure of the SHG-active sacran aggregates was modeled from the observed facts.