Abstract
We report on rotationally resolved laser induced fluorescence (LIF) and vibrationally resolved resonance-enhanced multiphoton ionization (REMPI) spectroscopy of the chiral molecule 1-indanol. Spectra of the S1← S0 electronic transition are recorded in a jet-cooled, pulsed molecular beam. Using two time-delayed pulsed lasers, the lifetimes of the S1 state of the two most stable conformers, referred to as eq1 and ax2, have been determined. The S1← S0 origin bands of these conformers as well as the transition to a vibrationally excited level in the S1 state of eq1 are recorded with full rotational resolution (25 MHz observed linewidth) by measuring the LIF intensity following excitation with a tuneable, narrowband cw laser. On selected rotationally resolved electronic transitions, Lamb-dips are measured to confirm the Lorentzian lifetime-contribution to the observed lineshapes. The rotationally resolved S1← S0 origin band of a neon-complex of eq1 is measured via LIF as well. The fit of the rotationally resolved LIF spectra of the origin bands to those of an asymmetric rotor yields a standard deviation of about 6 MHz. The resulting spectroscopic parameters are tabulated and compared to the outcome of ab initio calculations. For both conformers as well as for the Ne-eq1 complex, the geometric structures in the S0 and S1 states are discussed. For all systems, the transition dipole moment is mainly along the a-axis, the contributions along the b- and c-axes being about one order of magnitude smaller.
Highlights
The intermolecular forces between chiral molecules and their chiral surroundings play an important role in the molecular recognition that accompanies many biological processes.[1]
We report electronic spectra recorded in an apparatus that can perform both low-resolution resonanceenhanced multiphoton ionization (REMPI) and high-resolution laser induced fluorescence (LIF) measurements under identical conditions
It consists of a source chamber and a detection chamber in which both low and high resolution UV experiments can be performed under identical conditions
Summary
The intermolecular forces between chiral molecules and their chiral surroundings play an important role in the molecular recognition that accompanies many biological processes.[1] the efficacy of most drugs is intimately related to the chirality of their stereogenic centers.[2] Gas phase spectroscopy enables the exploration of chiral molecules in isolation, without interference from any physical medium. If desired, these chiral molecules can be complexed with other molecules, e.g. water, in order to study molecular solvation as a function of cluster size. The alicyclic ring can undergo large-amplitude puckering motion that results in two sets of conformations in which the O atom is either axial or equatorial (Fig. 1).[5,6] In addition, the OH group can take on different orientations due to its torsional degree of freedom
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