Abstract:Time-resolved Fourier-transform Raman spectra of the first singlet excited states of anthracene and deuterated anthracene have been measured with photoexcitation at 355 nm. Raman scattering was excited by 100-ps pulses at 1064 nm, resonant with the S 3 r S 1 transition. Continuous wave (CW) Fourier-transform Raman spectra were also measured for anthracene and anthracene-d 10 in the ground state. Ab initio calculations were carried out at the HF/6-31G and HF/6-31G* levels for the ground state and at the CIS/6-3… Show more
“…Recently, Iwata et al 17 have also reported the transient Raman spectrum of S 1 anthracene by using a similar experimental setup with a near-infrared sensitive ICCD detector and picosecond near-infrared laser pulses. The reported spectrum with a good S/N ratio agrees well with those previously observed by Jas et al 12 and our group. 13 …”
We have constructed two types of picosecond time-resolved Raman spectrometers with near-infrared excitation. One system is based on a step-scan Fourier transform (FT) interferometer equipped with a Ge detector, and the other system is based on a dispersive spectrometer equipped with an InGaAs array detector. For the former system with pulsed Raman excitation, we have developed a new method of signal processing. This method does not require synchronization among laser pulses for Raman excitation, the stepping of the step-scan interferometer, and the sampling of the analog-to-digital converter. In spite of large fluctuation in the probe-pulse energy, the ordinary FT-Raman spectra of samples in the ground electronic state can be obtained with satisfactory signal-to-noise ratios by the former system. By the latter system, picosecond transient Raman spectra have been obtained from the first excited singlet (S 1 ) state of 9-phenylanthracene and the second excited singlet (S 2 ) state of all-trans-b-carotene by using 388-nm light for photoexcitation and 1064-nm light for Raman excitation.
“…Recently, Iwata et al 17 have also reported the transient Raman spectrum of S 1 anthracene by using a similar experimental setup with a near-infrared sensitive ICCD detector and picosecond near-infrared laser pulses. The reported spectrum with a good S/N ratio agrees well with those previously observed by Jas et al 12 and our group. 13 …”
We have constructed two types of picosecond time-resolved Raman spectrometers with near-infrared excitation. One system is based on a step-scan Fourier transform (FT) interferometer equipped with a Ge detector, and the other system is based on a dispersive spectrometer equipped with an InGaAs array detector. For the former system with pulsed Raman excitation, we have developed a new method of signal processing. This method does not require synchronization among laser pulses for Raman excitation, the stepping of the step-scan interferometer, and the sampling of the analog-to-digital converter. In spite of large fluctuation in the probe-pulse energy, the ordinary FT-Raman spectra of samples in the ground electronic state can be obtained with satisfactory signal-to-noise ratios by the former system. By the latter system, picosecond transient Raman spectra have been obtained from the first excited singlet (S 1 ) state of 9-phenylanthracene and the second excited singlet (S 2 ) state of all-trans-b-carotene by using 388-nm light for photoexcitation and 1064-nm light for Raman excitation.
“…The pressure-induced frequency shift results are summarized in Table . The vibrational modes listed in Table are numbered and referenced by molecular symmetry; however, the crystal symmetry splits these modes into a g and b g factor group components. 3 The pressure-induced Raman frequency shift of several of the phonons of crystalline anthracene. 4 The pressure-induced Raman frequency shift of several of the vibrons of crystalline anthracene.…”
Pressure-induced Raman shifts and line broadening in crystalline anthracene have been studied up to 3.1 GPa
at ambient temperature. The use of nitrogen as a hydrostatic pressure medium eliminated pressure-induced
defect fluorescence that had previously restricted high-pressure Raman studies of anthracene. Mode Grüneisen
parameters have been determined for six phonons and nine vibrons, and some evidence for a previously
suggested phase transition at 2.4 ± 0.2 GPa is observed in the line width data. The calibrated pressure-induced spectral shifts and line width changes also can be utilized as a gauge of the pressure and temperature
profile of a laser-induced shock front (Hambir, S. A.; Franken, J.; Hare, D. E.; Chronister, E. L.; Baer, B. J.;
Dlott, D. D. J. Appl. Phys.
1997, 81, 2157).
“…22 These problems limit the application of time-resolved near-IR resonance Raman spectroscopy beyond the frequency region accessible by CCD to only a few cases. [23][24][25][26] When the sensitivity of spontaneous Raman spectrometers is limited by the Raman scattering probability and the performance of detectors, third-order nonlinear Raman spectroscopy can be a good technique for obtaining a spectrum equivalent to the spontaneous Raman spectrum. Stimulated Raman scattering (SRS, Fig.…”
Charge transfer and charge delocalisation processes play key roles in the functions of large biomolecular systems and organic/inorganic devices. Many of the short-lived transients involved in these processes can be sensitively detected by monitoring their low-energy electronic transitions in the near-IR region. Ultrafast time-resolved near-IR Raman spectroscopy is a promising tool for investigating the structural dynamics of the short-lived transients as well as their electronic dynamics. In this study, we have developed a femtosecond time-resolved near-IR multiplex stimulated Raman spectrometer using the Raman pump pulse at 1190 nm and a broadband probe pulse covering the 900-1550 nm region. Spectral and temporal instrument responses of the spectrometer are estimated to be 5 cm(-1) and 120 fs, respectively. Time-resolved near-IR stimulated Raman spectra of poly(3-dodecylthiophene) (P3DDT) are recorded in toluene solution for investigating its structural changes following the photoexcitation. The spectra strongly indicate conformational changes of P3DDT in excited states associated with the elongation of its effective conjugation length. The results on P3DDT fully demonstrate the effectiveness of the newly developed femtosecond time-resolved near-IR stimulated Raman spectrometer.
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