Transmission, nanosecond

All of the molecules in this study have triplet states which are easily detectable by the technique of nanosecond transmission laser flash photolysis. (11) The triplet state of acetoveratrone has a lifetime in excess of 15 ps in ethanol (Figure 2) under conditions of laser excitation the decay involves a mixture of first and second order kinetics, with the latter dominating at high laser powers. This second order decay demonstrates that the triplet state is decaying at least partly by triplet-triplet annihilation. 

TOL, toluene THF, tetrahydrofurane DMSO, dimethylsulfoxide CH3CN, acetonitrile CHC13, chloroform. TPEF, two-photon excited fluorescence WLC, white light continuum NLT, nonlinear transmission. cfs, femtosecond ps, picosencond ns, nanosecond. 

DMSO, dimethylsulfoxide TOL, toluene EtOH, ethanol THF, tetrahydrofiirane CH2C12, methylene chloride. TPEF, two-photon excited fluorescence NLT, nonlinear transmission fs, femtosecond ns, nanosecond. Wavelength used for excitation maximum is localized at other wavelength. 

Because of this wide range of applications, much effort was dedicated to the design and synthesis of new molecules with optimized TPA efficiency in this context, the characteristics of the designed molecules (linear absorption, solubility, substituents...) will depend on the targeted application. The TPA response of moleciUes can be imderstood in the context of its TPA cross-section ajpA. which can be measmed using different techniques, such as nonlinear transmission, two-photon induced fluorescence and the Z-scan method although in a pure TPA process ajpA does not depend on the laser pulse duration, the nonlinear absorption can be more efficient in the nanosecond regime than in the femtosecond one, due to excited state reabsorption phenomena [34]. 

The analysis of the transmission of the film during irradiation suggests that decomposition of the triazene chromophore occurs during irradiation. The decomposition of the chromophore in the film should result in changes of the surface topography. Therefore another time-resolved method was applied that can give this information. This technique is nanosecond interferometry, which allows the observation of the surface morphology with nanosecond resolution. 

One of the designed photolabile triazene polymers (Scheme 8) was selected to test whether a different behavior can be detected for these materials. In this report, decomposition dynamics of the photosensitive triazene polymer film upon intense XeF excimer laser irradiation is studied by applying the nanosecond interferometric technique with a newly improved optical setup. On the basis of the revealed morphological dynamics as well as the obtained time-resolved transmission and reflectance, the ablation mechanism and the dynamics of the triazene polymer film are discussed in detail. 

Figure 6 shows the dependence of the energy transmission through the samples as a function of the incident intensity. If nonresonant two-photon absorption were the only mechanism giving rise to the transmission drop, we would expect the nanosecond and the... 

Figure 6. Energy transmission of the samples measured as a function of the incident intensity. The circles and triangles repre.sent the daui for the polybcnzidinc sttmple for the nanosecond and the picosecond lasers, respectively.

A series of new ( )-4,4 -bis(diphenylammo)stilbene derivatives have been synthesized to investigate nonlinear absorptivities with attention paid to the peripheral substituent effect and multibranched modification effect by the open aperture femtosecond Z-scan technique and the nanosecond nonlinear optical transmission (NET), respectively [36]. Two-photon fluorescence for ( )-4,4 -bis(di-phenylamino)stilbene in THE was detected. It was found that substituent group attached to the periphery of BDPAS has no obvious contribution to TPA enhancement and that the dramatic increase in effective TPA cross sections of multibranched samples in nanosecond regime strongly suggested their larger excited-state absorption. 

Large-core multi-mode fibres are used for the transmission of laser radiation of short pulse duration (nanosecond and femtosecond pulses). 

---