Ultra-fast spectroscopy

M. Seel, E. Wildermuth, W. Zinth, A multichannel detection system for application in ultra-fast spectroscopy, Meas. Sci. Technol. 8 (1997) 449. 

Pulsed two-color mid-infrared ultra-fast spectroscopy was used to study the effect of ions on the structural dynamics of their aqueous solutions by Bakker s group [44]. The pump pulse that excited the 0-H (or 0-D) stretch vibration to the first excited state was provided first, and then after a short delay, the probe pulse, which was red-shifted with respect to the first, probed the decay of this state. Solutions of 0.5 to... 

Short laser pulses (ranging routinely from ps to ns) often offer advantages in analysis, e.g. the application of time-of-flight analysers. The application of ultra-fast spectroscopy based on new fs pulsed lasers has undoubtedly been one of the most significant innovations at the same time, the frequency stability of lasers is now in the mHz range. Demtroder [3] described time-resolved laser spectroscopy. Pulsed lasers are natural sources for time-resolved tluorime-try. 

Fleming, G. R., 1986, Chemincal applications of ultra fast spectroscopy. The international series of monographs on Chemistry, 13 124, Oxford University Press, New York. 

In previous work it has been shown that the width of the zero-phonon hole (ZPH) in the photochemical hole burned spectrum of the P-band can be used to determine the lifetime of P from its total zero-point level which, incidentally, is a determination not possible by ultra-fast spectroscopy. 

In addition to the surface/interface selectivity, IR-Visible SFG spectroscopy provides a number of attractive features since it is a coherent process (i) Detection efficiency is very high because the angle of emission of SFG light is strictly determined by the momentum conservation of the two incident beams, together with the fact that SFG can be detected by a photomultiplier (PMT) or CCD, which are the most efficient light detectors, because the SFG beam is in the visible region, (ii) The polarization feature that NLO intrinsically provides enables us to obtain information about a conformational and lateral order of adsorbed molecules on a flat surface, which cannot be obtained by traditional vibrational spectroscopy [29-32]. (iii) A pump and SFG probe measurement can be used for an ultra-fast dynamics study with a time-resolution determined by the incident laser pulses [33-37]. (iv) As a photon-in/photon-out method, SFG is applicable to essentially any system as long as one side of the interface is optically transparent. 

By means of femtochemistry, investigation of elementary reactions on a timescale of femtoseconds (10-15s) is possible. The method employs a combination of pulsed-laser and molecular-beam technologies. Investigation of a unimolecular reaction by femtosecond spectroscopy involves two ultra-fast laser pulses being passed into a beam of reactant molecules. 

Transient nvo-dirttcnsml infrared spectroscopy towards measuring ultra fast structural dy namics... 

To resolve excited state processes in terms of kinetics and spectroscopy the course of a reaction needs to be followed as a function of time. Charge transfer processes typically occur on picosecond to nanosecond time scales. To this end, ultra-fast... 

Solvation dynamics refers to the solvent reorganization or relaxation that accompanies the external excitation of a probe solute, usually a fluorescent organic dye or simply an excess solvated electron [55], Experimentally, the process of solvent reorganization can be time monitored by the time evolution of the fluorescence emission in time-dependent ultra-fast Stokes shift spectroscopy. 

The unique feature of ultra-fast MAS NMR spectroscopy is the possibility of using the band-selective CP experiment. This approach was recently reported by... 

Because of the use of TATP by terrorists, a reliable and fast detection of this material is desirable. In addition to conventional analytical methods such as mass spectrometry and UV (ultra violet) spectroscopy specially trained explosive detec-... 

Durrant and co-workers performed ultra-fast interfacial electron injection studies with cM-Ru(dcb)2(NCS)2-Ti02 in 1 1 ethylene carbonate-propylene carbonate solvent and were able to observe both the oxidized sensitizer and the electron in Ti02 by time-resolved absorption spectroscopy [202]. Unfortunately, at long observation wavelengths, X = 650-900 nm, these absorption features overlapped with each other, making assignments and analysis difficult. Detailed analysis of the transient absorption data indicate that the electron injection process is at least bi-phasic with 50 % injecting in less than 150 fs and 50 % in 1.2 ps. 

Gold received much attention due to their unique size-dependent optical properties, insolubility in nitric acid and resistance to heat, moisture, oxygen and most corrosive reagents. For substrates in surface-enhanced Raman Spectroscopy (SERS), ergonomic electronic contacts, ultra fast data communication and biomedicine surface modified gold nanoparticles are perspective agents, while in the industry of catalysis platinum nanoparticles (Pt NPs) exhibiting excellent anticorrosive and catalytic properties are usually employed. 

In femtosecond spectroscopy (Figures 7.7 and 7.8), an ultra-fast laser injects two pulses of radiation into a beam of reactant molecules. In the case of the investigation of a unimolecular reaction these are all of one type. For a bimolecular reaction the... 

A critical and most important problem that still remained to be solved was to find an adequate analytical methcxl that would enable us to follow in real time the kinetics of such ultra-fast polymerizations. Different techniques have already been used to study the laser-induced curing of acrylic monomers (DSC, IR spectroscopy, interferometry,...) but none of them provide conversion versus exposure time curves for polymerization that occur in a fraction of a second. The results obtained by some of these techniques are now briefly reported for comparison with those obtained by using real-time infra-red (RTIR) spectroscopy, a powerful method newly developed in our laboratory to investigate the kinetics of ultrafast photopolymerizations (0. 

Ian C. Stewart is a chemist for a petrochemical company. He formerly worked with Nobel Prize-winning chemist Robert H. Grubbs and is the recipient of several fellowships. Justin P. Lomont is a National Science Foundation Graduate Research Fellow whose doctoral research at the University of California, Berkeley focuses on organometallic reaction mechanisms using ultra fast infrared spectroscopy. 

J. Petitjean, J. Tanguy, J.C. Lacroix, K.I. Chane-Ching, S. Aeiyach, M. Delamar, and P.C. Lacaze, Interpretation of the ultra-fast electropolymerization of pyrrole in aqueous media on zinc in a one-step process The specific role of the sahcylate salt investigated by X-ray photoelectron spectroscopy (XPS) and by electrochemical quartz crystal microbalance (EQCM), J. Electroanal. Chem., 581, 111-121 (2005). 

---