Resonantly enhanced multiphoton ionization and zero kinetic energy photoelectron spectroscopy of 2-indanol conformers

Abstract

We report studies of a supersonically cooled 2-indanol using two-color resonantly enhanced multiphoton ionization (REMPI) and two-color zero kinetic energy (ZEKE) photoelectron spectroscopy. In the REMPI experiment, we have identified three conformers of 2-indanol and assigned the vibrational structures of the first electronically excited state for the two major conformers. Conformer Ia contains an intramolecular hydrogen bond between the -OH group and the phenyl ring, while conformer IIb has the -OH group in the equatorial position. We have further investigated the vibrational spectroscopy of the cation for the two major conformers using the ZEKE spectroscopy. The two conformers display dramatically different vibrational distributions. The ZEKE spectrum of conformer Ia shows an extensive progression in the puckering mode of the five member ring, indicating a significant geometry change upon ionization. The ZEKE spectra of conformer IIb are dominated by single vibronic transitions, and the intensity of the ZEKE signal is much stronger than that of conformer Ia. These results indicate an invariance of the molecular frame during ionization for conformer IIb. We have performed ab initio and density functional theory calculations to obtain potential energy surfaces along the dihedral angle involving the -OH group for all three electronic states. In addition, we have also calculated the vibrational distribution of the ZEKE spectrum for the puckering mode of the five member ring. Not only the vibrational frequencies but also the intensity distributions for both conformers have been reproduced satisfactorily. The adiabatic ionization energies have been determined to be 68 593+/-5 cm(-1) for conformer Ia and 68 981+/-5 cm(-1) for conformer IIb.

Zero kinetic energy photoelectron spectroscopy of jet cooled benzo[a]pyrene from resonantly enhanced multiphoton ionization

“…Unlike all the other PAH molecules we have studied, [16][17][18] a clear propensity of preserving the vibrational excitation of the intermediate state can be identified in the ZEKE spectra of BaP, with negligible vibrational relaxation or mode mixing. [35][36][37][38][39] When ambiguities arise in the assignment of combination bands, we therefore believe that the combination containing the original vibrational excitation is the most probable. Figure 4(a) was recorded via the origin of the S 1 state, and the most intense peak corresponds to the origin of the cation.…”

Photodissociation yield spectroscopy of vinyl bromide cation generated by mass-analyzed threshold ionization: Vibrational spectroscopy and decay dynamics in the B̃ state

“…[11][12][13][14] One advantage of the two-photon scheme is that the intermediate neutral state information can be utilized for identification of the final cation state. Since the lower wavelength limit of a commercial dye laser is around 210 nm, early ZEKE/MATI studies were done mostly for molecules with an ultraviolet ͑UV͒ chromophore, even though variations of the scheme such as 2 + 1 three-photon absorption could handle molecules without an UV chromophore.…”

Direct evidence for weak intramolecular O–H⋯π hydrogen bonding in 1-hydroxytetralin

“…The conformer IV seems to have such hydrogen, which should lead to the stability as predicted by the calculation. For hydroxyindans [9][10][11][12][13] and aminoindans [6,7,14] analyzed precisely, all the conformers identified as the most stable structure also have such hydrogen, whether or not it was recognized as the hydrogen bonding. These results strongly suggest that in 1HT the intramolecular hydrogen bonding between the hydroxyl hydrogen and the p-electron of the benzene ring attributes to the conformational stabilities, where the geometrical configuration (equatorial/axial) would also play an important role.…”

“…The stable conformers of substituted indans have been successfully identified by laser spectroscopy [6,7,[9][10][11][12]14]. The most stable conformer had a hydrogen pointing toward the benzene ring, which can be recognized as the hydrogen bonding.…”

“…Bicyclo compounds consisting of a benzene ring and a saturated five-or six-membered ring would be suitable to comprehend the properties of weak 'intramolecular' Y-HÁ Á Áp hydrogen bonding, since substitution of a functional group such as ÀCH 3 , ÀNH 2 , and ÀOH to the saturated ring gives rise to conformers involving different configurations (axial and equatorial) and orientation of the substituent [6][7][8][9][10][11][12][13][14]. The stable conformers of substituted indans have been successfully identified by laser spectroscopy [6,7,[9][10][11][12]14].…”