Doppler-Free Two-Photon Research Articles

Doppler-Free Two-Photon Excitation Spectroscopy and the Zeeman Effect in the “Channel Three” Region of C6H6

Abstract Doppler-free two-photon excitation spectra and the Zeeman effects for the 1021401 and 1011401 bands, whose vibrational excess energies are 3412 and 2492 cm−1, respectively, of the S11B2u ← S01A1g transition in gaseous benzene-h6 have been measured. Rotationally resolved lines up to a rotational excess energy of 945 cm−1 in the 1011401 band, whose excess energy is isoenergetic with the one of the 1021401 band at low J, have been observed. The density of perturbation is observed to increase around the K = 0 and K = J levels in the 1011401 band as the rotational energy increases, but line broadening is not observed. It was reported that only the K = 0 lines at low J and the K = J lines at high J were observed as a sharp line and the rest was washed out by broadening in the 1021401 band. The assignments are confirmed by the Zeeman spectra. The character and magnitude of Zeeman splittings in both bands could be understood as originating from the electronic orbital angular momentum arising from a mixing of the S11B2u and S21B1u states via J–L coupling. The levels of the S11B2u state are found not to be mixed with a triplet state by the Zeeman effect.

Doppler-free Two-Photon Spectroscopy of Benzene in a Cold Supersonic Beam

Doppler-free two-photon absorption is demonstrated for cold molecules in a supersonic beam with a spectral resolution of 10 MHz. It was realized using a frequency stabilized tunable external concentric resonator placed within the vacuum chamber and crossed by the molecular beam. The achieved high resolution allows us to resolve single rotational lines in the S

Determination of the D/T fuel mixture using two-photon laser induced fluorescence in combination with neutral beam injection

Doppler-free two-photon induced fluorescence in the Lyman-α lines of H, D, and T has been suggested previously as a local and isotope-selective diagnostic of the intrinsic neutral hydrogen densities in magnetically confined fusion plasmas. In the present article, it is shown that the diagnostic potential of this method is significantly increased if it is combined with neutral atom beams whose characteristics are such that efficient production of thermal ground state atoms via charge exchange reactions is achieved. Considerably deeper plasma regions than just the plasma edge can thus be probed and local, isotope-selective information (e.g., the H/D/T density ratios) is obtained on the more relevant ions rather than on the intrinsic neutrals. Additional diagnostic possibilities, e.g., those arising from the spectroscopic investigation of the beam particles themselves, are also discussed.

Doppler-free two-photon polarization-spectroscopic measurement of the Stark-broadened profile of the hydrogen L alpha line in a dense plasma.

It is demonstrated that Doppler-free two-photon polarization spectroscopy makes possible Stark profile measurements without Doppler-broadened background under high-density and high-temperature conditions, e.g., in dense arc plasmas, where other sub-Doppler laser-spectroscopic techniques introduced so far fail. This method, based on the polarization rotation connected with a two-photon transition, is not limited by collisions changing the velocity or the excitation of the atoms or by photoionization of the upper level.

Energy and radiative lifetime of the 5d96s2 2D5/2 state in Hg II by Doppler-free two-photon laser spectroscopy.

Energy and radiative lifetime of the 5d96s2 2D5/2 state in Hg II by Doppler-free two-photon laser spectroscopy.

Doppler-free two-photon absorption and dispersion spectroscopy with a Fabry-Perot cell

Infrared spectroscopy has been performed using a CO 2 laser and a Fabry-Perot resonator filled with SF 6 as absorber. Transmitted as well as reflected power displays sharp Doppler-free two-photon (DFTP) transitions of the 0–2v 3 SF 6 band. With the experimental set-up described, the DFTP dispersion can be easily observed. Owing to the saturability of the SF 6 absorber the Fabry-Perot resonances display dispersive bistability.

Doppler-Free Two-Photon Dispersion and Optical Bistability in Rubidium Vapor

Doppler-free two-photon dispersion has been observed in rubidium vapor near the $5{S}_{\frac{1}{2}}\ensuremath{-}5{D}_{\frac{5}{2}}$ two-photon transition. The experiment was performed by looking at the shape of the transmission peaks of a Fabry-Perot cavity filled with rubidium. When the nonlinear susceptibility is large, a bistable behavior occurs. A nonperturbative treatment of the susceptibility is required for the interpretation of these results.

Frequency Shifts, Line Broadenings, and Phase-Interference Effects in Rb**+Rb Collisions, Measured by Doppler-Free Two-Photon Spectroscopy

Self-broadenings and frequency shifts of ${n}^{2}S$ and ${n}^{2}D$ Rydberg levels (up to $n\ensuremath{\sim}70$) have been measured for rubidium in the pressure range of 3 to 100 mTorr, and the general dependence on principal quantum number $n$ has been established for this low-pressure regime. A closer examination has revealed large (almost evenly spaced) oscillations in the dependence of linewidth on principal quantum number for the $^{2}S$ levels in the region of largest linewidth ($n\ensuremath{\sim}20 \mathrm{to} 30$).

Raman transients observed in Doppler free two-photon excitation

Using Doppler-free two-photon excitation, we have observed the transients produced by the sudden introduction or cut-off of the exciting light. The two-photon excitation is of a particular interest because all the atoms are excited with the same energy detuning from the resonance. We have observed the time-variation of the scattered light for several values of the detuning. The corresponding results show the transition from resonance fluorescence to Raman scattering.

Observation of Ramsey's Interference Fringes in the Profile of Doppler-Free Two-Photon Resonances

Using two coherent time-delayed short pulses, we have demonstrated that one can obtain, in the profile of Doppler-free two-photon resonances, interference fringes with a splitting $\frac{1}{2T}$ ($T$, delay time between the two pulses) much smaller than the spectral width $\frac{1}{\ensuremath{\tau}}$ of each pulse ($\ensuremath{\tau}$ duration of each pulse). This method should lead to a number of important improvements in the presently available techniques of ultrahigh-resolution laser spectroscopy of atoms and molecules.