Measurement of the First-Excited-Singlet-State Lifetime of Chlorobenzenes by a Pump-Probe Method Using a Narrow-Band Tunable Picosecond Laser

Development of a Narrow-Band Tunable Picosecond Dye Laser and Its Application to Excited-State Lifetime Measurement of a Chlorinated Aromatic Hydrocarbon

“…Ref. 16). A picosecond Nd:YAG laser (Continuum, Leopard, 120 ps, 10 Hz) was employed as a pump source of the dye laser, in order to suppress additional peaks after a single isolated pulse generated using a nanosecond Nd:YAG laser.…”

“…The pulse width and line width of the laser were measured by means of a streak camera (Hamamatsu, C4334, resolution 15 ps) and a wavemeter (Burleigh Instruments, WA 5500, resolution 0.002 pm), respectively. A detailed description of the SSJ/MPI-MS instrument and the pump-probe method used in this study have been reported elsewhere 16 and are described briefly here. A block diagram of the scheme is shown in Fig.…”

“…This is much shorter than the values for the monochlorobenzene and dichlorobenzene. 16 Generally, an increase in the number of chlorine atoms substituted on a benzene ring decreases the lifetime of the excited state. This is known as a "heavy atom effect", which accelerates intersystem crossing, consequently causing poor efficiency in multiphoton ionization with a nanosecond laser source.…”

“…A distributed-feedback (DFB) dye laser, 11-13 which is tunable over a wide spectral region and capable of generating a picosecond pulse with a narrow spectral bandwidth, has the potential for application to SSJ/MPI-MS. 14, 15 We recently developed a DFB dye laser with a pulse width and line width of 160 ps and 9.64 pm, respectively, and used it to measure the excited-state lifetimes of monochlorobenzene and dichlorobenzene. 16 More recently, a DFB dye laser with a shorter pulse width (68 ps), which was achieved by a new type of quenching scheme, was developed.17 Therefore, a tunable picosecond laser with a shorter pulse width is useful not only for efficient ionization of molecules with shorter excited-state lifetimes but also for the excited-state lifetime measurement of these compounds.In this study, a transform-limited DFB dye laser with a shorter pulse width (< 25 ps) was developed, using a picosecond Nd:YAG laser as a pump source and employing a thinner cuvette for oscillation. The excited-state lifetime of a highly chlorinated benzene derivative, i.e., 1,2,4-trichlorobenzene, was then measured by means of a pump-probe method in SSJ/MPI-MS.…”

“…A picosecond Nd:YAG laser (Continuum, Leopard, 120 ps, 10 Hz) was employed as a pump source of the dye laser, in order to suppress additional peaks after a single isolated pulse generated using a nanosecond Nd:YAG laser. [14][15][16][17] In the oscillator stage, the third harmonic beam of the Nd:YAG laser was diffracted by a holographic transmission grating (500 groove/mm). The first-order diffracted beams were then combined with each other by means of two mirrors to form an interference pattern on the surface of the dye solution (Coumarin 153 in methanol) in a cuvette (2.5 mm).…”