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The structure of the 1-naphthol (NH[SUB3])[SUB2] cluster was investigated by rotational coherence spectroscopy (RCS), mass selective one- and two-color resonant two-photon ionization (R2PI) experiments and ab initio calculations. RCS measurements yielded rotational constants of 1-naphthol (NH[SUB3])[SUB2] as A = 1197, B = 500, and C = 413 MHz, as well as those for several isotopomers. The counterpoise-corrected second-order Mφller-Plesset perturbation theory (MP2) method predicts two isomers A and B. Both structures have hydrogen bonded naphthol-OH… NH[SUB3]… (NH[SUB3] chains, with the second NH[SUB3] (bent above the proximal aromatic ring and pointing towards the p-electron system and have nearly the same binding energy. The experimental rotational constants agree better with those calculated for structure B. The B3LYP and PW91 density functional methods also predict two isomers A, B with the rotational constants of B in acceptable agreement with experiment. Based on two-color R2PI experiments using low ionization frequency to suppress cluster fragmentation, the S[SUB1]←S[SUB0] electronic origin region of the 1-naphthol (NH[SUB3])] [SUB2 - 4] cluster series as reassigned, in agreement with the work of Dedonder-Lardeux et al. [Phys. Chem. Chem. Phys. 3, 4316 (2001)]. In one-color experiments, the 1-naphthol (NH[SUB3])[SUB3] cluster fragments with nearly 100% efficiency into the 1-naphthol (NH[SUB3])[SUB2SUP+] mass channel. [ABSTRACT FROM AUTHOR]

The results of nonlinear Raman experiments on two intermolecular bands of expansion-cooled naphthalene trimer at 0.03 cm-1 resolution are reported. The polarization and intensity dependences of the observed band contours strongly indicate that the observations pertain to transitions between pendular states that result from the interaction of a strong optical field and the permanent polarizability anisotropy of the trimer. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this and the accompanying paper we present a theoretical treatment and experimental study, respectively, of the phenomenon termed purely rotational coherence. This phenomenon has been demonstrated to be useful as a time domain means by which to obtain high resolution spectroscopic information on excited state rotational levels of large molecules [Felker et al., J. Phys. Chem. 90, 724 (1986); Baskin et al., J. Chem. Phys. 84, 4708 (1986)]. Here, the manifestations in temporally resolved, polarization-analyzed fluorescence of coherently prepared rotational levels in samples of isolated symmetric and asymmetric top molecules are considered. These manifestations, for reasonably large molecules at rotational temperatures characteristic of jet-cooled samples, take the form of polarization-dependent transients and recurrences with temporal widths of the order of tens of picoseconds or less. The transients, which arise from the thermal averaging of many single molecule coherences, are examined with respect to their dependences on molecular parameters (rotational constants, transition dipole directions) and experimental parameters (polarization directions and temperature). A physical picture of rotational coherence as a reflection of the time-dependent orientation of molecules in the sample is developed. And, the influence of rotational coherence in experiments designed to probe intramolecular energy flow is discussed. In the accompanying paper, we present experimental results for jet-cooled t-stilbene and anthracene. For t-stilbene we determine rotational constants for vibrational levels in the S1 electronic state (from the recurrences) and we monitor the trends in rotational coherence vs vibrational coherence as the total energy in the molecule increases. [ABSTRACT FROM AUTHOR]

The characteristics and origin of a new type of rotational coherence effect—asymmetry transients—are considered. Asymmetry transients are of two types, which we call C-type and A-type, respectively. C-type features are spaced by time intervals equal to 1/(4C). A-type features are spaced by time intervals equal to 1/(4A). Both types of transients can provide information on rotational constants that is not available from other types of rotational coherence effects. We show that the C-type transients arise from coherences between rotational eigenstates of the form Jτ and (J+2)τ-2 (in the Jτ notation) and that the A-type ones arise from coherences between eigenstates Jτ and (J+2)τ+2. The fact that such coherences produce asymmetry transients is shown to be a consequence of the limiting behavior of asymmetric top energy levels at high values of J. Experimental results in which asymmetry transients are present are reported for jet-cooled perylene, tryptamine (D conformer), 1-naphthol–water, and fluorene–benzene. [ABSTRACT FROM AUTHOR]

Theoretical and experimental results relating to the picosecond laser implementation of Fourier transform stimulated emission spectroscopy (FT-SES) and Fourier transform hole-burning spectroscopy (FT-HBS) in molecular beams are presented. It is shown that the resolution in the schemes is only limited by the length of the interferogram taken, and not by factors such as the excitation pulsewidths, excitation bandwidths, or the delay between the pump and probe laser pulses. In addition, the factors which determine the homogeneous and Doppler broadening in FT-SES and FT-HBS spectra are examined. It is found that ground-state damping factors determine the homogeneous broadening in FT-SES and excited-state damping factors determine such broadening in FT-HBS. Doppler broadening in both of the methods is shown to be that associated with two-photon resonant vibrational transition frequencies rather than one-photon resonant vibronic transition frequencies. The characteristics of the Fourier transform methods are compared to those of their frequency-domain counterparts. [ABSTRACT FROM AUTHOR]