Direct observation of the resonant-non-resonant cross-term contribution to coherent Raman scattering of quasi-continuous-wave noisy light in molecular liquids

Abstract

The resonant-non-resonant cross-term contribution to the coherent Raman scattering (CRS) signal produced by broadband non-transform limited quasi-cw (noisy) light is directly observed in the form of a spectrogram. The technique is a recently developed time-frequency domain version of CRS using noisy light. Vibrational modes of three (neat) molecular liquids were examined : the C-C stretching mode of acetone, the C-Cl stretching mode of methylene chloride and the "ring breathingÏ mode of cyclohexane. The resonant-non-resonant cross-term is revealed as a striking asymmetry in the observed time-frequency domain spectrogram. This is the analogue of the dispersive resonant-non-resonant cross-term in conventional CRS spectroscopy. However, unlike conventional CRS, noisy light interferometry yields a CRS spectrum that is uncoupled from the linewidth which instead governs the interferometric decay. The ratio of the resonant to non-resonant cross-term contribution can be quantiÐed and, as is well known, a reversible link between absolute Raman cross-sections and absolute non-resonant susceptibility of any chosen molecular liquid can be established.

Twin Markovian field correlation on four-level attosecond polarization beats

“…For the macroscopic system where phase matching takes place this signal must be drawn from the P (3) developed on one 'atom' multiplied by the (P (3) ) * that is developed on another 'atom' which must be located elsewhere in space (with summation over all such pairs) [16][17][18][19][20][21][22][23][31][32][33][34][35][36][37][38]. For homodyne detection the FASPB signal is proportional to the average of the absolute square of P (3) over the random variable of the stochastic process |P (3) | 2 , which involves fourth-and second-order coherence functions of u i (t) in phase-conjugation geometry.…”

“…By contrast, the first term with the factor exp −2 a 20 |τ | and the second term with the factor exp(−2α 3 |τ |) are ω 1 + ω 2 two-photon resonant NDFWM and ω 1 + ω 3 two-photon nonresonant NDFWM autocorrelation terms, respectively, while the third term is the ω 1 + ω 2 two-photon resonant NDFWM and ω 1 + ω 3 two-photon nonresonant NDFWM cross-correlation term in equation (34). Ulness et al [18] directly observed the resonant-nonresonant cross-term contribution to coherent Raman scattering of quasi-continuous-wave noisy light in molecular liquids.…”

“…It is interesting to understand the underlying physics in FASPB with broadband nontransformlimited quasi-cw (noisy) light [13]. Much attention has been paid to the study of various ultrafast phenomena by using incoherent light sources recently [16][17][18][19][20][21][22][23]. Beams 2 and 3 have broadband linewidths so the beams can be modelled as a sequence of short, phaseincoherent subpulses of duration τ c , where τ c is the laser coherence time [13].…”

“…For over a decade, ultrashort time resolution of material dynamics has been accomplished by the interferometric probing of wave mixing with broadband, nontransform-limited noisy light (one less direct method). The time resolution is determined by the ultrafast correlation time of the noisy light and not by its temporal envelope, which is typically a few nanoseconds [12][13][14][15][16][17][18][19][20][21][22][23]. Such a 'noisy' light source is usually derived from a dye laser modified to permit oscillation over almost the entire bandwidth of the broadband source.…”

On the Role of Classical Field Time Correlations in Noisy Light Spectroscopy: Color Locking and a Spectral Filter Analogy

“…This special issue will no doubt cover many of the areas of physical chemistry in which Professor Albrecht has contributed. The current paper deals with one of those areas: noisy light spectroscopy. − Professor Albrecht was one of the leaders of this interesting field from very early in its development to the present time, with most of his efforts coming from 1986−2001. Professor Albrecht published 30 papers and gave numerous talks on the subject of noisy light spectroscopy.…”