Femtosecond laser mass spectrometry

Intact molecular ion formation has a great advantage for application to femtosecond laser mass spectrometry (FLMS). The Ledingham group has used... 

Femtosecond photoionization mass spectrometry might be useful in the study of the three-dimensional structure of large biomolecules. When a selectively excitable and ionizable chromophore is located on the outer (surface) part of large molecule, one can be detached in the picosecond time scale. However, when the excitable chromophore is located in the inner part of the big molecule, its detachment will require a much longer time, which is needed for spatial rearrangement of the molecule. So, even the simple mass spectrometry of bioorganic molecules with femtosecond laser ionization can reveal some details of their spatial structure. 

In their recent landmark femtosecond-resolved mass spectrometry studies, Zewail and coworkers have used mass spectrometry for monitoring the time-resolved unimolecular fragmentation of neutral norbomene and norbomadiene. In both cases, the RDA reactions occurred, but only in the norbomadiene case was the well-known H loss giving rise to C7H7+ ions found to compete. Still, non-concertedness and biradicaloid character of the intermediates is being addressed by femtosecond dynamic studies. In this context, Kompa and coworkers" have compared the expulsion of H+ from femtosecond-laser-irradiated... 

Poitrasson, X.L., Mao, S.S., Freydier, R., Russo, R.E. 2003. Comparison of ultraviolet femtosecond and nanosecond laser ablation inductively coupled plasma mass spectrometry analysis in glass, monazite, and zircon. Analytical Chemistry, 75, 6184-6190. 

G. Gerber At moderate laser intensities we do see in femtosecond pump-probe experiments a very similar slow time and long time dynamics in all cluster sizes n > 5 up to n = 50 (largest size investigated up to now) irrespective of the charge state of the particular Hg cluster. From single-pulse TOF mass spectrometry we infer that the... 

Figure 7. Time-resolved mass spectrometry. AU-trcms-(2, 4, 6, 8) decatetraene was excited to its 5 2 electronic origin with a femtosecond pulse at A-pump — 287 nm. The excited-state evolution was probed via single-photon ionization using a femtosecond pulse at ApIObe = 235 nm. The time resolution in these experiments was 290 fs (0.3 ps). The parent ion CioH signal rises with the pump laser, but then seems to stay almost constant with time. The modest decay observed can be fit with a single exponential time constant of 1 ps. Note that this result is in apparent disagreement with the same experiment performed at Xprobe — 352 nm, which yields a lifetime of 0.4 ps for the S2 state. The disagreement between these two results can be only reconciled by analyzing the time-resolved photoelectron spectrum.

Detection and identification of chemical warfare simulants based on multidimensional phase shaped femtosecond laser pulses coupled to mass spectrometry (MS) is demonstrated. The presented approach is based on binary phase shaping (BPS) and aims to improve the accuracy and precision required for security applications. It is based on multiphoton intrapulse interference of femtosecond laser pulses. Spectra retrieved by applying n-differently shaped pulses represent n-dimensions of the analysis. We present a multidimensional technique for detection and identification of analogues to chemical agents and mixtures in real-time. Experimental results for dimethyl phosphate, pyridine, and three isomers of nitrotoluene are presented. 

Laser ionization mass spectrometry of explosives and chemical warfare simulants has been studied using nanosecond laser pulses. Primary ions observed in many of these studies were NO and PO, which are not unique signatures of the parent molecules. It is now widely accepted that after absorption of the first photon, the parent molecule dissociates on a time scale of about 100 femtoseconds (fs). We can attempt to compensate for this rapid dissociation by using ultrafast laser pulses of a corresponding time duration." Here we compare the nanosecond, ultrafast, and SPI approaches. 

Chinese gold with femtosecond laser ablation-inductively coupled mass spectrometry. Journal of Archaeological Science 36(2) 461-466. 

Transient intermediates are most commonly observed by their absorption (transient absorption spectroscopy see ref. 185 for a compilation of absorption spectra of transient species). Various other methods for creating detectable amounts of reactive intermediates such as stopped flow, pulse radiolysis, temperature or pressure jump have been invented and novel, more informative, techniques for the detection and identification of reactive intermediates have been added, in particular EPR, IR and Raman spectroscopy (Section 3.8), mass spectrometry, electron microscopy and X-ray diffraction. The technique used for detection need not be fast, provided that the time of signal creation can be determined accurately (see Section 3.7.3). For example, the separation of ions in a mass spectrometer (time of flight) or electrons in an electron microscope may require microseconds or longer. Nevertheless, femtosecond time resolution has been achieved,186 187 because the ions or electrons are formed by a pulse of femtosecond duration (1 fs = 10 15 s). Several reports with recommended procedures for nanosecond flash photolysis,137,188-191 ultrafast electron diffraction and microscopy,192 crystallography193 and pump probe absorption spectroscopy194,195 are available and a general treatise on ultrafast intense laser chemistry is in preparation by IUPAC. 

Figure 8 Positive ion mass spectra taken from sinapinic acid using primary ion beam sputtering and laser postionization with 15 ns (A) and 500 fs (B) pulses of A = 248nm. (Reprinted from Mdllers R, Terhorst M, Niehuis E, and Benninghoven A (1992) Resonant photo-ionisation of sputtered organic molecules by femtosecond LIV laser pulses. Organic Mass Spectrometry 27 1393-1395.)...

Over the past three decades the combination of pulse (e.g., femtosecond) lasers with MS has attracted considerable attention (for an overview, see [20]). TRMS has found applications in the studies of desorption processes induced by energetic light beams. As an illustration. Van Breemen et al. [21] investigated desorption of non-volatile organic salts following a laser pulse. The desorbed species were further analyzed by time-of-flight mass spectrometry (TOF-MS). von der Linde and Danielzik [22] demonstrated MS detection in... 

Gas chromatography/time-of-flight mass spectrometry of triacetone triperoxide based on femtosecond laser ionization. Rapid Commun. Mass Spectrom., 23, 3101-3106. 

Koch, I, Gunther, D. (2007) Femtosecond laser ablation inductively coupled plasma mass spectrometry achievements and remaining problems. Analytical and Bioanalytical Chemistry, 387,149-153. 

Brostoff, L., Gonzalez, L, Jett, R, Russo, R. (2009) Trace element fingerprinting of ancient Chinese gold with femtosecond laser ablation-inductively coupled mass spectrometry. Journal of Archaeological Science, 36, 461 66. 

Hergemoder, R., Samek, O., and Hommes, V. (2006) Femtosecond laser ablation elemental mass spectrometry. Mass Spectrom. Rev., 25, 551-572. 

Koch, )., Walle, M., Pisonero,)., and Gunther, D. (2006) Performance characteristics of ultra-violet femtosecond laser ablation inductively coupled plasma mass spectrometry at -265 and -200 nm. J. Anal. At. 

Hirata, T. and Kon, Y. (2008) Evaluation of the analytical capability of NIR femtosecond laser ablation-inductively coupled plasma mass spectrometry. 

Investigation on elemental and isotopic fractionation during 196 nm femtosecond laser ablation multiple collector inductively coupled plasma mass spectrometry. Spectrochim. Acta B, 62, 410-422. 

The goal of this book is to present in a coherent way the problems of the laser control of matter at the atomic-molecular level, namely, control of the velocity distribution of atoms and molecules (saturation Doppler-free spectroscopy) control of the absolute velocity of atoms (laser cooling) control of the orientation, position, and direction of motion of atoms (laser trapping of atoms, and atom optics) control of the coherent behavior of ultracold (quantum) gases laser-induced photoassociation of cold atoms, photoselective ionization of atoms photoselective multiphoton dissociation of simple and polyatomic molecules (vibrationally or electronically excited) multiphoton photoionization and mass spectrometry of molecules and femtosecond coherent control of the photoionization of atoms and photodissociation of molecules. 

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