Tracking molecular wave packets in cesium dimers by coherent Raman scattering

Abstract

We explore wave-packet dynamics in the ground X 1 + g and excited B 1 u states of cesium dimers (Cs 2 ). In particular, we study the dependence of the wave-packet dynamics on the relative timing between femtosecond pump, Stokes, and probe pulses in a nondegenerate BOXCARS beam geometry, which are commonly used for coherent anti-Stokes Raman scattering (CARS) spectroscopy. The experimental results are elucidated by theoretical calculations, which are based on the Liouville equations for the density matrix for the molecular states. We observe oscillations in CARS signals as functions of both Stokes and probe pulse delays with respect to the pump pulse. The oscillation period relates to the wave-packet motion cycle in either the ground or excited state of Cs 2 molecules, depending on the sequence of the input laser pulses in time. The performed analysis can be applied to study and/or manipulate wave-packet dynamics in a variety of molecules. It also provides an excellent test platform for theoretical models of molecular systems.

Multiple pathway quantum beat spectroscopy

“…It is also possible to detect the beat pattern by monitoring the transmission of the infrared probe [14] as well as X-ray absorption [28], as long as different quantum pathway interferences at a common final state are realized [24,29]. Controls of the beat pattern and thus the quantum path have been studied in our group by shifting the pump wavelength [15] or adding a control pulse [4]. In the present case, a shift of the pump beam central wavelength would tune the amplitudes and initial phase of the beat pattern.…”

“…Quantum coherence plays important roles in many advances in quantum detection and control techniques in the recent two decades, such as coherent anti-Stokes Raman scattering (CARS) spectroscopy [1,2], multidimensional Fourier transform spectroscopy [3], wave packet control of atoms and molecules [4][5][6], and quantum interference control of photocurrent [7], due to the fact that optical interference can reveal the quantum pathways in which the system evolves. Quantum computers also heavily rely on coherent manipulation of quantum states, for e.g., in atomic, ionic, and superconducting circuit qubits [8][9][10].…”