Femtosecond degenerate four‐wave mixing study of benzene in the gas phase

Abstract

We report on time-resolved rotational spectroscopy of benzene molecules both in a gas cell at room temperature (298 K) and in a supersonic expansion (30 K) by femtosecond degenerate four-wave mixing (fs-DFWM). A detailed study of the time-dependent structure of the rotational recurrences for the gas cell is presented. Moreover, for the first time, the fs-DFWM technique has been applied to a medium-sized molecule in the collision-free environment of a seeded supersonic expansion up to a time delay of 4 ns. From these data, by fitting of the experimental spectra, a rotational constant B = 5688.95 ± 0.55 MHz was obtained for benzene in the gas cell and B = 5689.25 ± 0.11 MHz for benzene in the supersonic expansion. The combination of gas cell and supersonic jet investigations by fs-DWFM provides a means for the structural study of large and more complex molecules.

Rotational constants and structure of para-difluorobenzene determined by femtosecond Raman coherence spectroscopy: A new transient type

“…6-8,13,14,17-20, [25][26][27][28][29][30][31][32][33][34][35] In off-resonant four-wave mixing -which is appropriate here, since p-DFB is com-pletely transparent at the 800 nm laser wavelength -the DFWM signal of the gas sample is proportional to the square modulus of its time-dependent third-order susceptibility, [36][37][38] χ (3) (t), which can be written as…”

Time domain fingerprints of a ‘perpendicular’ rotational Raman band: formic acid studied by femtosecond degenerate four‐wave mixing

“…A stronger influence, however, of the CDs can be seen at longer time delay, manifested in a rich modulation pattern. 8 In order to learn in general about the influence of molecular asymmetry and CDs on the rotational recurrence periods, one can invoke the available theoretical approaches. 1,17,18 We start from the analysis of K-transients.…”

“…5,8 A femtosecond CPA system is used at the fundamental wavelength (800 nm, 150 fs pulse duration, 1 kHz repetition rate). The output is split into three identical beams that are focused into the sample cell, providing the phase-matching condition for the so-called forward boxcar configuration of four-wave mixing.…”

Formation of coherent rotational wavepackets in small molecule-helium clusters using impulsive alignment

“…When used with long laser pulse, the technique is often refereed as adiabatic alignment [3][4][5]9 , whereas for pulse duration shorter than the rotational period of the molecule, impulsive or field-free alignment is a common term. The impulsive alignment technique is derived from the well-known rotational coherence spectroscopy method that has been intensively applied to the investigation of the rotational structure of free molecules [10][11][12][13][14] , clusters [15][16][17] and liquids 18 . Laser-induced impulsive alignment can be applied to all molecules with an anisotropy of polarisability.…”