Ground state vibrational wave‐packet and recovery dynamics studied by time‐resolved CARS and pump‐CARS spectroscopy

Abstract

Recent experiments on gaseous iodine and b-carotene are analyzed within a wave-packet description of femtosecond-time resolved four-wave mixing spectroscopy. Employing the same formalism, two different experimental setups, both established in the Kiefer group, are treated. In a transient four-wave-mixing (FWM) experiment, where two pulses interact simultaneously with the system, the interaction with a third time-delayed pulse leads to light emission reflecting ground state vibrational dynamics in I 2 . On the other hand, delaying a FWM-pulse sequence with respect to a single pump pulse interacting with b-carotene yields a signal that is directly proportional to the population of a selected nuclear eigenstate in the electronic ground state. Thus, within this setup, it is possible to monitor ground-state re-population dynamics mode specifically.

Ultrafast time-resolved vibrational spectroscopies of carotenoids in photosynthesis

“…These results show good agreement with those determined independently using femtosecond timeresolved Raman spectroscopy [21,23]. Siebert et al applied pump-CARS measurement to β-carotene, in which pre-pump laser pulse was introduced before starting the CARS measurement, and reported the relationship between the relaxation of excitation energy and molecular vibrations [82][83][84]. According to the series of studies, they concluded that the C_C stretching vibration (1524 cm −1 ) has the largest contribution as the accepting mode for excitation energy, and the other modes have the similar but less contribution in the order, C\C stretching (1157 cm −1 ), C\CH 3 rocking (1004 cm −1 ), C_C\C bending (872 cm −1 ), and C\H bending (1269 cm −1 ).…”

Probing the geometry dependence of molecular dimers with two-dimensional-vibronic spectroscopy

“…19 In the present paper we employ a wave function based description of optical vibronic 2D spectroscopy and treat a coupling to an environment only phenomenologically. Although this is, ultimately, not satisfactory from a theoretical point of view, we feel that the basic notions of the spectra ͑applying equally to the characterization of time-resolved four-wave mixing signals [20][21][22] ͒ can be explained simpler than within the more involved density matrix description.…”

Raman spectroscopy at the beginning of the twenty‐first century

“…The experimental results are impressive, having the CARS signal measured over 7 decades of intensity. The paper by Siebert et al 50 presents interesting new results of FWM experiments onˇ-carotene and gas-phase iodine. Time-resolved CARS and pump-CARS techniques are employed as a tool to monitor ground-state vibrational dynamics of molecular iodine and population recovery ofˇ-carotene, respectively.…”