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She, C. Y.

Publications and source records attributed to She, C. Y..

24 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Measuring the velocity of individual atoms in real time

It is proposed that the thermal velocity of a single atom could be measured in real time using a laser time-of-flight velocimeter (LTV) operating on the principle of laser resonance fluorescence. Theoretical data are presented for several atomic species that have resonances within the range of available dye-laser systems. It is shown that measurements in the subsonic region are certainly feasible. The atoms could be either in vacuum or in a buffer gas, e.g., at atmospheric pressure. Measurements in the transonic and supersonic region also appear possible. One potential application is the measurement of flow speeds in wind tunnels, perhaps as high as Mach 45.

She, C. Y.↗
NASA NTRS1976

IR pumped third-harmonic generation and sum-frequency generation in diatomic molecules

The potential efficiency of using nonlinear up-conversion techniques for the high efficiency type lasers (CO,CO2, and chemical) is assessed. Results indicate that: the small pump photon energy necessitates the use of molecular media for conversion if resonance enhancement is to be used and that molecular systems present several problems. These difficulties include: their levels are complex; their transition probabilities are often unknown; and the oscillator strengths among vibrational levels in the ground electronic state of a molecule are much smaller than those among electronic states of an atom, thus limiting the magnitude of nonlinear interactions. It is shown that this problem can be eliminated by making use of vibronic transitions which, being primarily electronic transitions have much larger matrix elements and efficient conversion can be achieved with molecular systems.

She, C. Y.↗
NASA NTRS1975

Infrared-pumped third-harmonic and sum-frequency generation in diatomic molecules

Using molecular hydrogen as a model system, we present a calculation which demonstrates the feasibility of efficient third-harmonic and sum-frequency generation of IR laser radiation by diatomic molecular gases. A conversion efficiency of 10% without phase matching is achievable with a modest laser intensity of about 20 MW/sq cm. In addition to a two-photon resonance, the efficient conversion depends on a mechanism which makes use of virtual vibronic transitions exclusively. Possible methods for phase matching are also suggested.

She, C. Y.↗