The new technique of cavity enhanced velocity modulation spectroscopy has been further developed, incorporating a tighter cavity to laser lock and an optical frequency comb for absolute frequency calibration. Several N2 transitions have been observed with much higher precision than previously possible, and transitions that were blended in earlier Doppler-limited experiments are now resolved. Th...

The Kerr nonlinear index of refraction for rubidium atoms is measured by using an optical ring cavity with and without electromagnetically induced transparency (EIT). Significant enhancement and inhibition of the Kerr nonlinear index is observed near resonance with EIT. The nonlinear index of refraction is measured as functions of probe and coupling frequency detunings, respectively, with and w...

An echelle diffraction grating and a multianode photomultiplier tube are paired to construct a high resolution R= / 2.5 104 spectrograph with fast time response for use from the UV through the visible. This instrument has analyzed the line shape of C III impurity ion emission at 229.687 nm over the lifetime 100 s of the hydrogen plasmas produced at SSX. The ion temperature and line of sight ave...

We report the first observation of electron momentum contributions to the Doppler broadening of radiation produced by in-flight two-photon annihilation in solids. In these experiments an approximately 2.5 MeV positron beam impinged on thin polyethylene, aluminum, and gold targets. Since energetic positrons easily penetrate the nuclear Coulomb potential and do not cause a strong charge polarizat...

We employ an alternative technique for determining the Lorentzian linewidth based upon the simultaneous measurement of the vapor transmission and group-velocity delay outside the Doppler core of an optically dense transition. We apply this technique to measure the cross sections for broadening of the intercombination lines of calcium, 4s 'S0~4s4p Pi, and strontium, Ss 'S0~5s5p Pi, by collisions...

We demonstrate a new method for measuring translational temperatures using degenerate four-wave mixing (DFWM). We perform high-resolution measurements of DFWM spectra in both the forward (BoxCARS) and backward (phase-conjugate) phase-matching geometries on nitric oxide (NO) in a room-temperature gas cell. We analyze the spectra with a modified perturbation theory to extract the temperature from...

We present a quantum-mechanical calculation of Stark linewidths from electron-ion collisions for the 2s1/2-2p1/2,3/2 , l52066 and 2067 Å, resonance transitions in B III. The results confirm previous quantummechanical R-matrix calculations, but contradict recent measurements and semiclassical and some semiempirical calculations. The differences between the calculations can be attributed to the d...

Two-photon Laser induced fluorescence diagnostics system for atomic oxygen has been installed at the 750kW arc heated wind tunnel in JAXA in order to obtain velocity, translational temperature, and number density of atomic oxygen simultaneously. It was observed that the center of excitation wavelength is shifted in the shock layer. The Doppler shift due to the free stream velocity has a same or...

A generalized least-square method with Tikonov–Miller regularization and non-negativity constraints has been developed for deconvoluting two-dimensional coincidence Doppler broadening spectroscopy ͑CDBS͒ spectra. A projected Newton algorithm is employed to solve the generalized least-square problem. The algorithm has been tested on Monte Carlo generated spectra to find the best regularization par...