DEVELOPMENT OF A HIGHLY-SENSITIVE ANALYTICAL INSTRUMENT FOR THE DETERMINATION OF ORIENTED MOLECULES USING A LASER FOR EXCITATION.

Development of a new highly-sensitive and informative analytical instrument is a key target of the modern analytical chemistry。A second harmonic light beam of the incident laser is produced when the laser irradiate a sample of unsymmetrical orientation。This principle may be used for determination of adsorbed molecules at the air-liquid surface and liquid-liquid interface.A new instrument was constructed by using a goniometer and precision stage，which were purchased by the grant。The incident angle of the laser to the surface could be controlled arbitaray，and the angular dependence of the second harmonic generation could be easily measured.Thus，the determination of molecular orientation could be carried out without assumption and the selection of the optimum incident angle for an analytical purpose could be easily found.An improvement of the laser two-photon ionization instrument was carried out by using a new power supply unit，which was purchased by the grant。Application of a higher votage increased the collection efficiency of electric charge and enhanced the sensitivity.The typical detection limits of the new and revised instruments are as follows：Laser two-photon ionization method···Pyrene on water····0.2fmol····BBQ on metal···0.1pmol Laser second-harmonic generation···DEOC on glass····0.2pmol These values are better than prefficiency and the pititivity.

Development of a new highly-sensitive and informative analytical instrument is a key target of the modern analytical chemistry. A second harmonic light beam of the incident laser is produced when the laser irradiate a sample of unsymmetrical orientation. This principle may be used for determination of adsorbed molecules at the air-liquid surface and liquid-liquid interface.A new instrument was constructed by using a goniometer and precision stage, which were purchased by the grant. The incident angle of the laser to the surface could be controlled arbitaray, and the angular dependence of the second harmonic generation could be easily measured. Thus, the determination of molecular orientation could be carried out without assumption and the selection of the optimum incident angle for an analytical purpose could be easily found.An improvement of the laser two-photon ionization instrument was carried out by using a new power supply unit, which was purchased by the grant. Application of a higher votage increased the collection efficiency of electric charge and enhanced the sensitivity.The typical detection limits of the new and revised instruments are as follows : Laser two-photon ionization method・・・・・・Pyrene on water・・・・・・0.2fmol・・・・・・BBQ on metal・・・・・・0.1pmol Laser second-harmonic generation・・・・・・DEOC on glass・・・・・・0.2pmol These values are better than previous investigations and the initital purpose of the project has been approximately fulfillled.