Doppler-free Two-photon Spectra Research Articles

Doppler-Free Two-Photon Spectroscopy of 6S1/2–6D3/2,5/2Transition in Cesium

The Doppler-free two-photon spectra of the 6 S 1/2 ( F = 3)–6 D 3/2 ( F = 2 to 5), 6 S 1/2 ( F = 4)–6 D 3/2 ( F = 2 to 5), 6 S 1/2 ( F = 3)–6 D 5/2 ( F = 5 to 1) and 6 S 1/2 ( F = 4)–6 D 5/2 ( F = 6 to 2) transitions in cesium are observed using a titanium-sapphire laser. These spectra can be used as an optical frequency standard. The hyperfine coupling constants A (magnetic dipole constant) and B (electric quadrupole constant) are determined using spectral line splittings, giving A = 16.17(17) MHz and B = 0.11(127) MHz for the 6 D 3/2 state, and A =-4.56(9) MHz and B = -0.35(183) MHz for the 6 D 5/2 state.

Doppler-free two-photon spectrum of SF_6 for metrological purposes

We report on our systematic investigation of strong Doppler-free two-photon absorption in the middle infrared. The absorption frequencies for two counterpropagating waves of identical frequencies are predicted. Five of these transitions were observed with sub-Doppler resolution with a sideband CO(2) laser and were measured with 10-kHz accuracy. Knowledge of these strong two-photon absorptions frequencies will allow the improvement of secondary frequency standards in the infrared.

Doppler-free two-photon spectrum of the 0 00 band of the à 1B 1←X̃ 1A 1 transition in difluorodiazirine, F 2CN 2

The Doppler-free two-photon excitation spectrum of the vibrationless à 1B 1←X̃ 1A 1 transition of difluorodiazirine (F 2CN 2) has been recorded with a resolution of 15 MHz using a cw single-mode dye laser coupled to an external concentric resonator. The asymmetric rotor spectrum has been analysed and more than 350 lines randomly selected from all five branches were assigned in order to fit the ground- and excited-state rotational and quartic centrifugal distortion constants. From the rotational constants the r NN and r FF distances in the ground X̃ 1A 1 and excited à 1B 1 state were determined. The geometry change upon excitation is found to be Δ r NN = 3.89(2) pm and Δ r FF = −4.09(2) pm. No perturbation in the rotational structure of the 0 0 0 band has been found. This points to a small singlet-triplet coupling matrix element in the small molecule limit.

Doppler-free two-photon spectroscopy of the 2 ν3 band of SF 6

The assignments of most of the observed Doppler-free two-photon spectra of the 2 ν 3 band of SF 6 near the P(14)– P(20) lines of a 10-μm CO 2 waveguide laser are reported. The rovibrational and anharmonic constants for this band were obtained, along with ground state constants determined from observed “forbidden” transitions.

Heterogeneous perturbations in the Doppler-free S 1 ← S 0 two-photon spectrum of benzene: Evidence for intrastate coupling

Rotational perturbations are identified in Doppler-free two-photon spectra of the 14 1 0 and 14 1 01 1 0 vibronic bands in C 6H 6. Evidence is found that Coriolis coupling between some of the rotational levels of two distinct vibrational states within S 1 is the mechanism responsible. This coupling mechanism is thought to be responsible for irreversible intramolecular relaxation at higher excess energies and higher vibrational state densities.

Doppler-free two-photon spectroscopy using degenerate four-wave mixing

Using recently developed techniques of degenerate, four-wave mixing, Doppler-free two-photon spectra can be obtained. The signal level for such an experiment in xenon is calculated and found to be readily detectable as well as competing favorably with the method of observing fluoresence following two-photon absorption.

ʌ-type doubling and spin-rotation splitting of NO, measured in simultaneous one- and two-photon laser spectroscopy

Doppler-free two-photon excitation of NO A 2Σ + by visible dye laser radiation is recorded simultaneously with single-photon absorption of frequency-doubled UV laser light. The measurement of the frequency difference between corresponding lines in the one- and two-photon spectrum provides a new method for a direct optical determination of Λ-type doubling in the X 2Π ground state. In addition, the spin-rotation splitting of the A 2Σ + excited state is resolved in the Doppler-free two-photon spectrum.