Decay traces at 600 and 780 nm probe wavelengths measured usingsingle-channel detection and excitation at 400 nm wavelength with ∼1.3 mJ/cm2 fluence. The monotonic component of the photoinduced response was fitted (dashed line) according to Eq. (2) . The residual (dotted line) represents mainly the oscillating part, which is due to coherent A 1 g phonons. Fitting parameters are shown in the tables.
Decay traces measured at three values of pump fluence. The inset shows the curves in a semilogarithmic scale with oscillations filtered out (prior to normalization the traces were shifted to equalize their quasiconstant σ 3 components).
Decay traces measured using pump fluences of 0.3 and 0.05 mJ/cm2 at 800 nm probe wavelength. Dashed lines indicate the difference of monotonic components at early delay times. A slower rise at the low excitation intensity reflects the initial electronic dynamics, which limits the efficiency of coherent phonon generation.
Decay traces measured with 400 nm (solid line) and 2300 nm (dashed line) excitation pulses. The probe wavelength was 800 nm (fixed). The inset shows pump photon energy dependence of the initial amplitude of oscillations Aosc (squares), the amplitude of the 1 ps component σ 1 (circles), and the maximum phase shift Δϕ of coherent oscillations due to the variation of instantaneous frequency (crosses). Certain temporal resolution and the duration of pump pulses were taken into account. Dashed lines are guides to the eye.
A part of the band structure of bismuth adapted from Ref. 44 . Filled arrow shows resonant excitation of electrons leading to the appearance of the fast 1 ps component and effective generation of coherent A 1 g phonons. Empty arrow stands for “below-threshold” transitions which cause the accumulation of charge carriers near the Fermi level. Dashed regions correspond to excited electrons (L point) and holes (T point) having the nanosecond lifetime. Dotted arrows are transitions leading to the relaxation of photoexcited species (cooling and recombination).
Spectra of the amplitude of coherent oscillations A(λ) and of the fast (σ 1) and quasiconstant (σ 3) components of the photoinduced response. The results are based on our previous study, 35 where the multichannel pump-probe system was used (at 1.8 mJ/cm2 excitation fluence).
Decay traces measured at 1.3 mJ/cm2 excitation fluence at probe wavelengths of 600 and 780 nm. The step of the delay line was as large as 5 ps; therefore, coherent oscillations were not resolved.
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