Stark control

The modification of the electronic potentials due to the interaction with the electric field of the laser pulse has another important aspect pertaining to molecules as the nuclear motion can be significantly altered in light-induced potentials. Experimental examples for modifying the course of reactions of neutral molecules after an initial excitation via altering the potential surfaces can be found in Refs 56, 57, where the amount of initial excitation on the molecular potential can be set via Rabi-type oscillations [58]. Nonresonant interaction with an excited vibrational wavepacket can in addition change the population of the vibrational states [59]. Note that this nonresonant Stark control acts on the timescale of the intensity envelope of an ultrashort laser pulse [60]. 

For dynamics of even shorter durations, when the frequency of the external field is such that the time scale of the oscillation of the field is comparable to the time scale of nuclear dynamics, it may be better to regard the potential surfaces as becoming time-dependent through including the interaction potential within them [355]. The potential surfaces time-evolve not only with the envelope function of the external field but follows the oscillation of the external field itself, enabling dynamic Stark control [404]. 

Many of the hydrocarbons were similar to those identified in butter fat by Urbach and Stark (31), and some of these were concentrated up to 6-fold in fraction FI compared to the unextracted control. 

Among the terpenoids, phyte-l-ene, neophytadiene, phyte-2-ene and famesol were all highly concentrated in fraction FI compared to the non-extracted control. These compounds were previously associated with beef flavor i Larick et aL (52) and by Peterson and Chang (55). They were also identified in butter fat by Urbach and Stark (31) and in lamb by Suzuki and Bailey (25). Concentration of some of these compounds correlate highly with gras flavor of beef. 

While the formalism of DD is quite different from the formalism presented here, it can be easily incorporated into the general framework of universal dynamical decoherence control by introducing impulsive PM. Let the phase of the modulation function periodically jump by an amount 4> at times r, 2t,. .. Such modulation can be achieved by a train of identical, equidistant, narrow pulses of nonres-onant radiation, which produce pulsed AC-Stark shifts of co. When (/> = tt, this modulation corresponds to DD pulses. 

We have demonstrated a strong-held control scenario based on the SPODS. We derived the theoretical background in terms of both classical physics and quantum mechanics. We showed tunability of this bidirectional Stark effect up to nearly 300 meV, a selectivity of almost up to 100% and a precision down to the sub-10 as regime experimentally on atoms and molecules with a theoretical efficiency up to 100%. 

A 10 gram sample was placed in a 200 ml round bottom flask and 100 ml of distilled water added. A Dean-Stark trap and condenser were used and the mixture was brought to a boil. The steam distilled oil was measured after four hours versus control mixtures. In order to measure surface oil on the spray-dried powders, the powder was first washed with a solvent (ethyl ether or hexane) then oil retentions were run by the steam distillation method illustrated above. Differences in oil volume for solvent washed versus non-washed were attributed to surface oil on the spray-dried powders. 

More interestingly, it was found that in the condensation of allylstannane 191 with a-alkoxyaldehyde 193, the stereochemistry of the final adduct could be controlled by the amount of Lewis acid employed. Remarkably, if one equivalent of SnCl4 is used, the anti-homoallylic alcohol 194 is produced exclusively (Scheme 13.68) [87]. In stark contrast, if two equivalents of SnCl4 are employed, the reaction produces only the syn-homoallylic alcohol 195. 

---