New spectroscopy of water using tunable picosecond pulses in the infrared

Abstract

Spectral hole burning is observed for the OH stretching mode of HDO dissolved in D2O at 298 K after intense infrared excitation. Three spectral components are inferred from the transient band shapes and related to an icelike molecular environment and other hydrogen-bonding configurations. A population lifetime of T\ =8 ± 2 ps and an anharmonic frequency shift of 270 ± 20 cm ~] are measured.PACS numbers: 61.25. Em, 33.20.Ea, 42.65.Ft, 78.47.+p It is commonly believed that the properties of the OH stretching vibration are strongly related to the structure of the hydrogen bridge bond. Vibrational spectroscopy was, therefore, widely used in the past to investigate hydrogen-bonded systems. 1 For some liquids, e.g., alcohols, ir-absorption studies allow the determination of a few different hydrogen-bonded species and of the corresponding association parameters. 2 Matrix isolation techniques show that a larger number of transition frequencies can be discerned. 3 The relation of these observations to liquids is not well understood. For water, the situation is particularly complicated, since each molecule can form up to four hydrogen bonds. Several attempts have been reported to deduce structural information on this system from infrared, Raman, or attenuated-totalreflectance spectroscopy. 4 These results gave some evidence for a discrete substructure of the OH absorption that was attributed to different hydrogen-bonded environments. A final answer to such questions is still lacking; obviously more powerful spectroscopic techniques are required, e.g., time-resolved infrared spectroscopy 5 as demonstrated very recently for a H-bonded polymer. 6 In this Letter spectral hole burning on the picosecond time scale is reported for the first time for the vibrational spectrum of HDO dissolved in D2O. Direct evidence is obtained for a discrete substructure of the OH stretching band at 3400 cm" 1 . Three spectral components are deduced from the transient band shapes supporting a multicomponent model of water. 7 Details of the experimental system were described recently. 5 In short, a first intense ir pulse (energy -50 juJ, duration 11 ±2 ps, bandwidth 18 ±2 cm" 1 around 3400 cm -1 ) is tuned to the desired excitation frequency and resonantly pumps the OH stretching mode. A second, independently tunable, weak pulse probes the sample transmission T(VJD) as a function of delay time to or probe frequency v; to = 0 marks the maximum of the pump pulse. Most of the measurements are performed with parallel polarization of the excitation and interrogation pulses. The common small-signal transmission To(v) is measured blocking the pump beam.The samples (length 100 //m) were 0.5-1 mol/1 HDO in D2O prepared by mixing corresponding amounts of demineralized, bidistilled H2O in highly purified D 2 0 (99.996% isotopic purity). After proton exchange, the residual H2O content of the samples was less than 0.01 mol/1. Figure 1 (a) shows the absorption band of a HDO sample (1 mol/1, experimental points) obtained by a commercial infrared spectrometer a...

Azide–water intermolecular coupling measured by two-color two-dimensional infrared spectroscopy

“…[7][8][9][10][11][12][13][14][15][16][17][18][19][20] This is since the hydroxyl stretch has been directly associated with hydrogen bonding strength and thus providing a means to observe the bond strength between the ion and water. [21][22][23] Therefore, it is a suitable "sensor" for any rearrangement within the ion's solvation shell.…”

Probing the hydrogen-bond network of water via time-resolved soft X-ray spectroscopy

“…Static x-ray spectroscopy has revealed quantitative information on local atomic structure 4,5 whereas time-resolved vibrational spectroscopy has produced information on timescales of structural dynamics as short as 50fs. 6,7,8,9 Time-resolved vibrational spectroscopy has concentrated on the infrared spectrum of HOD in D 2 O and H 2 O 10,11,12,13,14,15,16 and to a lesser extent on pure H 2 O, 17,18 limited by the (sub-)micron absorption length. The latter also poses a challenge for x-ray absorption spectroscopy.…”

Vibrational Dephasing Mechanisms in Hydrogen-Bonded Systems

“…Vibrational phase relaxation in condensed phases has received considerable attention in recent decades because it is recognized as a powerful probe of intermolecular interaction dynamics [1]. Recent developments in timeresolved spectroscopy have allowed for, e.g., the measurement of homogeneous vibrational line shapes with IR transient hole-burning techniques [2,3] and the timeresolved observation of vibrational dephasing by means of a photon-echo experiment [4]. A great number of sophisticated models have been developed to describe vibrational line shapes [5][6][7][8][9][10], some specifically addressing the effect of hydrogen bonds [8][9][10].…”