Four-wave mixing signals from β-carotene and its n = 15 homologue

Abstract

The third-order nonlinear optical responses of beta-carotene and its homologue having a conjugation-double bond n = 15 have been investigated using sub-20 fs ultra-short optical pulses in order to clarify the dissipation processes of excess energy. Using the four-wave mixing spectroscopy, we observed a clear coherent oscillation with a period of a few tens of femtoseconds. The spectral density of these molecules was estimated that allowed the theoretical linear and nonlinear optical signals to be directly compared with the experimental data. Calculations based on the Brownian oscillator model were performed under the impulsive excitation limit. We show that the memory of the vibronic coherence generated upon the excitation into the S(2) state is lost via the relaxation process including the S(1) state. The vibronic decoherence lifetime of the system was estimated to be 1 ps, which is about 5 times larger than the life time of the S(2) state ( approximately 150 fs) determined in previous studies. The role of coherence and the efficient energy transfer in the light-harvesting antenna complexes are discussed.

Ultrafast time-resolved vibrational spectroscopies of carotenoids in photosynthesis

“…FWM signals in carotenoids are reported for β-carotene and its homologues, lycopene, astaxanthin, and spheroidene [47,[57][58][59][60][61][62][63][64][65][66][67][68]. As an example, the results of β-carotene are shown here.…”

Transient grating spectroscopy in photosynthetic purple bacteria Rhodobacter sphaeroides 2.4.1

“…This model has successfully explained the TG signals from b-carotene and its homologues [6][7][8]. In this study, we extend the model to the carotenoid molecules bound to the LH2 complexes.…”

“…We have so far studied the coherent signals from photosynthetic pigments [5][6][7][8]. The availability of femtosecond pulses allows the use of time-resolved spectroscopic techniques to observe the evolution of spectra in ''real time'' (see, for example, [9][10][11][12][13][14][15][16][17]).…”

Spectrally‐resolved transient grating signals from β‐carotene in benzene solution

“…The rise constituent is less prominent on decreasing the excitation frequency. The coherent oscillations were clearly observed when the excitation wavelength is set to the isosbestic point (curve B) which is the excitation condition of our previous studies [10][11][12]. The coherent oscillations and slowly-varying background become weak when the excitation wavelength is on the longer wavelength side (curves C to D).…”

“…As can be seen, when the TG signal of β-carotene is measured near the absorption edge (more correctly, when pumped at the isosbestic point), the experimental result is well reproduced using Eq. (1) [10][11][12]. However, in the impulsive limit the TG signal does not depend on the excitation wavelength, whereas the experimental results clearly show a strong excitation wavelength dependence (see Fig.…”