Simultaneous absorption

Multiphoton Absorption and Ionization. High laser powers can induce the simultaneous absorption of two or more photons that together provide the energy necessary to excite a transition this transition may be one that is forbidden as a single-photon process (8,297). Such absorption can be made Doppler-free by propagating two laser beams of frequency V in opposite directions, so the Doppler shifts cancel and a two-photon transition occurs at 2v for any absorber velocity. The signal is strong because aU absorbers contribute, and peak ampHtudes are enhanced by, which may... 

Simultaneous Absorption of Two Reacting Gases In multi-component physical absorption the presence of one gas often does not affect the rates of absorption of the other gases. When chemical reactions in which two or more gases are competing for the same hquid-phase reagent are involved, selectivity of absorption can be affected by... 

Figure 1.3. Real-time femtosecond spectroscopy of molecules can be described in terms of optical transitions excited by ultrafast laser pulses between potential energy curves which indicate how different energy states of a molecule vary with interatomic distances. The example shown here is for the dissociation of iodine bromide (IBr). An initial pump laser excites a vertical transition from the potential curve of the lowest (ground) electronic state Vg to an excited state Vj. The fragmentation of IBr to form I + Br is described by quantum theory in terms of a wavepacket which either oscillates between the extremes of or crosses over onto the steeply repulsive potential V[ leading to dissociation, as indicated by the two arrows. These motions are monitored in the time domain by simultaneous absorption of two probe-pulse photons which, in this case, ionise the dissociating molecule.

The NIR femtosecond laser microscope realized higher order multi photon excitation for aromatic compounds interferometric autocorrelation detection of the fluorescence from the microcrystals of the aromatic molecules confirmed that their excited states were produced not via stepwise multiphoton absorption but by simultaneous absorption of several photons. The microscope enabled us to obtain three-dimensional multiphoton fluorescence images with higher spatial resolution than that limited by the diffraction theory for one-photon excitation. 

Anthraquinones are nearly perfect sensitizers for the one-electron oxidation of DNA. They absorb light in the near-UV spectral region (350 nm) where DNA is essentially transparent. This permits excitation of the quinone without the simultaneous absorption of light by DNA, which would confuse chemical and mechanistic analyses. Absorption of a photon by an anthraquinone molecule initially generates a singlet excited state however, intersystem crossing is rapid and a triplet state of the anthraquinone is normally formed within a few picoseconds of excitation, see Fig. 1 [11]. Application of the Weller equation indicates that both the singlet and the triplet excited states of anthraquinones are capable of the exothermic one-electron oxidation of any of the four DNA bases to form the anthraquinone radical anion (AQ ) and a base radical cation (B+ ). 

When a droplet falling at a certain velocity impacts on an object, it will wet and spread through the surface if the contact angle is less than 90°. If the object is very thin, the droplet may all soak into it and the liquid may reach the other side that can be seen if the droplet contains a tracer dye. In a thick and porous Kromekote card,l507] a droplet spreads to form a circular stain with simultaneous absorption and penetration into the card. Kromekote cards have been used in forestry spray trials to collect pesticide droplets for... 

In conventional fluorescence spectroscopy, a fluorophore is excited by absorption of one photon whose energy corresponds to the energy difference between the ground state and the excited state. Excitation is also possible by the simultaneous absorption of two photons of lower energy (i.e. of longer wavelength) via a short-lived virtual state (Figure 11.4)3). For instance, absorption of two photons in the red can... 

Doppler-free two-photon spectroscopy spect A version of Doppler free spectroscopy in which the wavelength of a transition Induced by the simultaneous absorption of two photons is measured by placing a sample In the path of a laser beam reflected on itself, so that the Doppler shifts of the Incident and reflected beams cancel. dap-lor fre tu fO,tan spek tras-ka-pe j... 

An application for multiplexed diode-laser sensors with a potentially large impact is for measurements of important parameters at several locations in a gas turbine combustion system. In this example, illustrated schematically in Fig. 24.1, the multiplexed diode lasers are applied for simultaneous absorption measurements in the inlet, combustion, afterburner, and exhaust regions. For example, measurements of O2 mass flux at the inlet may be determined at the inlet from Doppler-shifted O2 absorption lineshapes near 760 nm. Measurements of gas temperature and H2O concentrations in the combustion and afterburner regions may be determined from H2O lineshape measurements near 1.4 pm. Finally, measurements of velocity, temperature, and species concentrations (e.g., CO, CO2, unburned hydrocarbons) may be recorded in the exhaust for the determination of momentum flux (component of thrust) and combustor emissions. 

A more sophisticated mode of LIE detection is the multiphoton-excitation (MPE) fluorescence [47], which is based on the simultaneous absorption of more than one photon in the same quantum event and uses special lasers, such as femtosecond mode-locked laser [48] or continuous wave laser [49], This mode of LIE detection allows mass detection limits at zeptomole level (1 zepto-mole=10 mol) due to exceptionally low detection background and extremely small detection volume, whereas detection sensitivity in concentration is comparable to that of traditional LIE detection modes. A further drawback is the poor suitability of MPE-fluorescence detection to the on-column detection configuration, which is frequently employed in conventional LIE detection. 

In most luminescence experiments, at least in the mineral luminescence field, excitation is due to absorption of a single photon. However, it is also possible for a luminescence center to absorb two or more long-wavelength photons to reach the excited state. Two-photon excitation occurs by the simultaneous absorption of two lower-energy photons. Such excitation requires special conditions including high local intensities, which can only be obtained from laser sources. 

The phenomenon of two-photon absorption (2 PA) can be presented as a process of simultaneous absorption of two photons under high intensity irradiation, resulting in one excited molecule [Ij. The investigations of 2PA previously undertaken are of great interest for a wide variety of emerging applications [3,36-42]. The nature of 2PA can be described based on the interaction of molecular electrons with an optical field. On a microscopic level the displacement of molecular electronic charge under the electric field, E, is related to the induced molecular dipole moment fi ... 

The crucial prerequisite of quantum Uthography is simultaneous absorption of N correlated photons in an N-photon absorbing material. We will discuss TPA of entangled photon pairs along the lines pursued in the literature [71-73]. Entangled photon absorption is often explained by com-... 

Another nonlinear absorption mechanism in dye molecules that becomes important at high light intensities is the simultaneous absorption of two photons of energy E = hv to reach a stationary energy level, situated at 2E, in the dye. This effect... 

Spray a mixture of the Macol 40 and water onto the Tetrasodium Pyrophosphate (alone or mixed with the other anhydrous inorganic salts) while continually mixing, whereby hydration and simultaneous absorption of the surfactant occur. 

Numerous attempts have been made to modify the original radiation theory by assuming the mechanism of activation to consist in (1) the simultaneous absorption of several quanta of different frequencies or the absorption Phys. Rev., 1924, 23, 693. 

From 200 to 242 nm, the 02 absorption, which is related to the Herzberg continuum with low absorption cross section, occurs in the stratosphere. In this spectral region, the ozone absorption must be introduced since the 03 Hartley band is characterized by high values of the absorption cross section between 200 and 300 nm. The simultaneous absorption by 02 and 03 must be considered in the stratosphere, whereas the O3 absorption is practically negligible in the mesosphere since the total number of absorbing ozone molecules is small. 

Sustained commercial application, however, did not occur until 1997, when Zheng et al. (7) described the successful stripping of oxygen from water used in secondary oil field recovery. In 1999 Trent et al. (8,9) introduced the first commercial application involving simultaneous absorption, reaction, and stripping. Both of these involve gas/liquid contact using a woven wire screen for the rotor internals. 

In TPA induced fluorescence spectroscopy the excited state population for fluorescence is created by the simultaneous absorption of two photons instead of the one-photon absorption in standard fluorescence experiments. The principles of this technique are described in Ref. [23]. It allows an experimental determination of two-photon absorption cross-sections provided the material is fluorescent and that its two-photon fluorescence quantum efficiency is known (which is usually assumed to be equal to the one-photon fluorescence quantum efficiency if the same excited state is reached). In this case the method generally provides high sensitivity. 

The simultaneous absorption of H2S and CO2 into aqueous 2.0 H diisopropanolamine (DIPA) solutions is studied both experimentally and theoretically. 

In this investigation we carried out experiments with simultaneous absorption of H2S and CO2 into aqueous 2.0 M diisopropanol-amine (DIPA) solutions at 25 °C. The results are evaluated by means of our mathematical mass transfer model both in penetration and film theory form. The latter version has been derived from the penetration theory mass transfer model [5],... 

If the amine depletion in the penetration zone in a simultaneous absorption situation is negligible, the mass transfer fluxes are independent of each other and the respective enhancement factors may be obtained easily from analytical solutions of single gas mass transfer models. 

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