Thermodynamics of adiabatic feedback control

We study adaptive control of classical ergodic Hamiltonian systems, where the controlling parameter varies slowly in time and is influenced by system's state (feedback). An effective adiabatic description is obtained for slow variables of the system. A general limit on the feedback induced negative entropy production is uncovered. It relates the quickest negentropy production to fluctuations of the control Hamiltonian. The method deals efficiently with the entropy-information trade off.Comment: 6 pages, 1 figur

INTRACAVITY LASER SPECTROSCOPY OF EXCITED ATOMS AND MOLECULES

The research described in this publication was made possible in part by Grant N NY3000 from the International Science Foundation.Author Institution: Institute of Atmospheric Optics, 634055 Tomsk, RussiaIntracavity laser (ICL) spectroscopy is a perspective method for investigation of atoms and molecules with different external excltation condition because of its high sensitivity to absorption, amplification, and small size of the investigated volume. ICL-spectrometers based on Nd-glass and dye broad-bands lasers have been designed with pulse duration 2000 and 100 microsecond, respectively. Those allow one to record absorption or amplification coefficients as small as $5 \times 10^{-9}$ and $10^{-7} cm^{-1}$ corresponding to 500,000 and 10000 path lengths used in traditional spectroscopy. Different techniques were used in our experiments for exciting molecules and atoms; these included heating up to 1200 K, atomization with a laser, hollow cathode atomization, and excitation with a discharge plasma. Large number of absorption and emission lines were recorded in atomic and electronic molecular spectra. The complicated character of ICL-spectra is connected to the fact that the broad-band laser provides the realization of conditions for laser generation in a wide region: $^{\ast}\hbox{COEFFICIENT OF AMPLIFICATION = COEFFICIENT OF RESONATOR LOSSES}^{\ast}$ As a result, any absorption (emission) line with Kabs (Kamp) more than $10^{-7} cm^{-1}$ inside the resonator cavity leads to the deep dips (sharp peaks) in the spectrum of the laser generation. Results obtained In this investigation were used to measure low concentrations of atoms. For example, the detection limit for the U-atom is $107 atoms/cm^{-3}.