Ueber den Nachweis und die Bestimmung der Milchs?ure

Ohne Zusammenfassung     

Single-molecule linewidths of terrylene in incommensurate biphenyl: Thermocycling and time-resolved experiments

The purely electronic linewidth δ of terrylene impurity molecules in monocrystalline biphenyl is studied at temperatures T between 1.7 and 3.5 K using the technique of single-molecule spectroscopy (SMS). Based on the data obtained, individual molecules appear to have their own law of δ(T) dependence; further, hysteresis effects have been observed in thermocycling experiments. The single-molecule (SM) lines investigated quickly broaden and vanish at temperatures between 3 and 3.5 K and reappear after the sample is cooled down again. At T≈2 K, a slow process of spectral diffusion (SD) was observed on timescales longer than 10 s. To learn about the role of faster SD processes, the technique of intensity-time-frequency correlation (ITFC) SMS was applied to a stable SM line after it had been broadened by 75% as a result of a thermocycling experiment. At 2 and 2.3 K, no significant line broadening could be revealed on timescales between 0.16 ms and 10 s.     

Remarks on certain growth conditions in problems of optimal control

In the Tonelli-Nagumo existence theorem for free problems of the calculus of variations, a uniform growth condition (T ₁) was employed to prove the equiabsolute continuity of the trajectories of a minimizing sequence. This same growth condition was shown to be equivalent to a pointwise growth condition (T ₂). Cesari utilized a generalization, condition (), in order to extend the Tonelli-Nagumo existence theorem to optimal control problems.In the present paper, we show that, for problems of optimal control, condition () is equivalent to a uniform growth condition () and that both conditions () and () are stronger than a pointwise growth condition (), a generalization of condition (T ₂). Two situations are given where conditions (), (), and () are equivalent, and the result of Tonelli and Turner concerning the equivalence of conditions (T ₁) and (T ₂) is obtained as a particular case of one of these situations.This research was partially supported by the National Science Foundation, Grant No. GK-234.     

Vibrational energy storage in high pressure mixtures of diatomic molecules

CO/N₂, CO/Ar/O₂, and CO/N₂/O₂ gas mixtures are optically pumped using a continuous wave CO laser. Carbon monoxide molecules absorb the laser radiation and transfer energy to nitrogen and oxygen by vibration–vibration energy exchange. Infrared emission and spontaneous Raman spectroscopy are used for diagnostics of optically pumped gases. The experiments demonstrate that strong vibrational disequilibrium can be sustained in diatomic gas mixtures at pressures up to 1 atm, with only a few Watts laser power available. At these conditions, measured first level vibrational temperatures of diatomic species are in the range T_V=1900–2300 K for N₂, T_V=2600–3800 K for CO, and T_V=2200–2800 K for O₂. The translational–rotational temperature of the gases does not exceed T=700 K. Line-of-sight averaged CO vibrational level populations up to v=40 are inferred from infrared emission spectra. Vibrational level populations of CO (v=0–8), N₂ (v=0–4), and O₂ (v=0–8) near the axis of the focused CO laser beam are inferred from the Raman spectra of these species. The results demonstrate a possibility of sustaining stable nonequilibrium plasmas in atmospheric pressure air seeded with a few percent of carbon monoxide. The obtained experimental data are compared with modeling calculations that incorporate both major processes of molecular energy transfer and diffusion of vibrationally excited species across the spatially nonuniform excitation region, showing reasonably good agreement.