Strong field effects in rotational femtosecond degenerate four-wave mixing

Abstract

We study theoretically strong field effects in rotational femtosecond degenerate four-wave-mixing (DFWM). First, we developed a perturbative approach and calculated the leading correction to the standard (weak field) formula for femtosecond DFWM signal. Second, we constructed a nonperturbative approach for computing femtosecond DFWM signals excited by (short) pulses of arbitrary intensity. Third, we worked out the theory to describe femtosecond DFWM with an extra aligning pulse. We show that the strong-pulse-induced nonadiabatic alignment does explain many experimentally detected features that develop in femtosecond DFWM signals with increasing laser intensity beyond the standard weak field regime. However, we also show that this nonadiabatic alignment cannot solely be responsible for the onset of the heterodyne detection and pronounced constant background in DFWM signals excited by high intensity laser pulses.

The conformational stability of gaseous 1-butene studied by femtosecond nonlinear spectroscopy and ab initio calculations

“…The energy of the probe was set to be twice as large as that of the pump pulse. This allows for increasing the four-wave mixing signal without disturbing it by high pump energies [18]. The probe pulse is delayed with respect to the pump pulses by a computer controlled translational stage, which allows the scanning of the time delay up to 4 ns.…”

Measurement of field-free alignment of jet-cooled molecules by nonresonant femtosecond degenerate four-wave mixing

“…(b) The evolution of cos 2 θ (t) from the same calculation. centrifugal distortion of the molecules, and any strong field effects in the DFWM process [30,31]. Based on the calculation, the maximum cos 2 θ value is 0.51 for the initial alignment peak.…”

Strong-pump strong-probe spectroscopy: effects of higher excited electronic states

“…Eqn (A8) and (A9) do not yield the final expression for the SPSP signal, since S(T) in eqn (A7) is determined by the total polarization P(t) rather than by the SPSP polarization P PP (t) which obeys the phase-matching condition (14). The D operator (A8) depends exclusively on pulse #1 and is k 1 -dependent.…”

“…Several groups have explored the phenomena induced by short and strong pulses in various material systems, ranging from diatomics to biomolecules and nanosystems [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] and several simulations of four-wave-mixing (4WM) signals beyond the weak-pulse limit have been reported. 5,[22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] Strong-field control of molecular population transfer [38][39][40] and of other photophysical and photochemical processes (ref.…”