Iodine excitation

These assignments assume that for CH3I and C2HSI the main and smaller peaks are I and I respectively and that the n-C3H7l peak is I. For iso-C3H7l, where the probable iodine excitation is less clear, the peak is analyzed twice first, assuming it is I and secondly assuming it is I. 

In a similar investigation, the interactions of the halogenomethanes CFgH, CH3F, and CH3CI with molecular iodine excited with 185 nm radiation have been studied in an attempt to elucidate the mechanisms of reactions of excited iodine molecules. ... 

Figure Al.6.20. (Left) Level scheme and nomenclature used in (a) single time-delay CARS, (b) Two-time delay CARS ((TD) CARS). The wavepacket is excited by cOp, then transferred back to the ground state by with Raman shift oij. Its evolution is then monitored by tOp (after [44])- (Right) Relevant potential energy surfaces for the iodine molecule. The creation of the wavepacket in the excited state is done by oip. The transfer to the final state is shown by the dashed arrows according to the state one wants to populate (after [44]).

Steinfeld J I and Klemperer W 1965 Energy-transfer processes in monochromatically excited iodine molecules. I. Experimental resulted. Chem. Phys. 42 3475-97... 

Plenary 11. W Kiefer et al, e-mail address wolfgang.kiefer mail.imi-wue.de (TR CARS). Ultrafast impulsive preparation of ground state and excited state wavepackets by impulsive CARS with REMPI detection in potassium and iodine duners. 

This technique with very high frequency resolution was used to study the population of different hyperfme structure levels of the iodine atom produced by the IR-laser-flash photolysis of organic iodides tluough multiphoton excitation ... 

As an example, we mention the detection of iodine atoms in their P3/2 ground state with a 3 + 2 multiphoton ionization process at a laser wavelength of 474.3 run. Excited iodine atoms ( Pi/2) can also be detected selectively as the resonance condition is reached at a different laser wavelength of 477.7 run. As an example, figure B2.5.17 hows REMPI iodine atom detection after IR laser photolysis of CF I. This pump-probe experiment involves two, delayed, laser pulses, with a 200 ns IR photolysis pulse and a 10 ns probe pulse, which detects iodine atoms at different times during and after the photolysis pulse. This experiment illustrates a frindamental problem of product detection by multiphoton ionization with its high intensity, the short-wavelength probe laser radiation alone can photolyse the... 

Unlike the situation regarding the crossing between the Vq and Fj potentials for Nal (see Figure 9.41), that for NaBr results in very efficient and rapid dissociation to give Na + Br when it is excited to Fj. Flow would you expect the fluorescence intensity from the neutral bromine atoms to vary with time compared with that for iodine atoms from Nal in Figure 9.42 ... 

Reactions that proceed photochemically do not necessarily involve observations of an excited state. Long before observations are made, the excited state may have dissociated to other fragments, such as free radicals. That is, the lifetime of many excited states is shorter than the laser excitation pulse. This statement was implied, for example, by reactions (11-46) and (11-47). In these systems one can explore the kinetics of the subsequent reactions of iodine atoms and of Mn(CO)s, a 17-electron radical. For instance, one can study... 

A dilute I2/CCI4 solution was pumped by a 520 nm visible laser pulse, promoting the iodine molecule from its ground electronic state X to the excited states A,A, B, and ti (Fig. 4). The laser-excited I2 dissociates rapidly into an unstable intermediate (I2). The latter decomposes, and the two iodine atoms recombine either geminately (a) or nongeminately (b) ... 

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.

In principle, all elements can be determined by AAS, since the atoms of any element can be excited and are therefore capable of absorption. The limitations lie practically only in the field of instrumentation. Measurements below 200 mn in the vacuum UV range are difficult, owing to the incipient absorption of atmospheric oxygen. With modified instruments and a shielded flame or a graphite furnace, it is possible to determine such elements as iodine at 183.0 nm, sulfur at 180.7 nm, and phosphorous at 177.5 nm, 178.3 nm and 178.8 nm. 

It is unlikely that the compound (27) is derived directly from the reaction of an excited benzene with tetrafluorobenzyne even though the compound (27) is formally analogous to the photo-adducts formed by the irradiation of olefins in benzene 74,75) A number of other products derived from the o-iodotetrafluorophenyl radical were also obtained 73>. These results suggest either that the tetrafluoro-o-phenylene di-radical (32) is identical with tetrafluorobenzyne or that if it is produced at a higher energy level it returns rapidly to the groundstate before it reacts with benzene. An alternative and perhaps more likely explanation is that the tetrafluorobenzyne formed arises by the concerted loss of both iodine atoms. 

As it concerns the band in the UV region (at 315 nm in the present case), Benesi and Hildebrand [5] assigned this absorption to a charge-transfer transition, where the phenyl ring acts as an electron donor (D) and the iodine as an electron acceptor. The interaction can be described in resonance terms as D-I2 <-> D+I2", the band being assigned to the transition from the ground non polar state to the excited polar state. 

Soon after Dennison had deduced from the specific-heat curve that ordinary hydrogen gas consists of a mixture of two types of molecule, the so-called ortho and para hydrogen, a similar state of affairs in the case of iodine gas was demonstrated by direct experiment by R. W. Wood and F. W. Loomis.1 In brief, these experimenters found that the iodine bands observed in fluorescence stimulated by white light differ from those in the fluorescence excited by the green mercury line X 5461, which happens to coincide with one of the iodine absorption lines. Half of the lines are missing in the latter case, only those being present which are due to transitions in which the rotational quantum number of the upper state is an even integer. In other words, in the fluorescence spectrum excited by X 5461 only those lines appear which are due to what we may provisionally call the ortho type of iodine molecule. 

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