Photodissociation resonances of jet-cooled NO2 at the dissociation threshold by CW-CRDS.

Around 398 nm, the jet-cooled-spectrum of NO2 exhibits a well identified dissociation threshold (D0). Combining the continuous-wave absorption-based cavity ringdown spectroscopy technique and laser induced fluorescence detection, an energy range of ∼25 cm(-1) is analyzed at high resolution around D0. In addition to the usual molecular transitions to long-lived energy levels, ∼115 wider resonances are observed.

Internal rotation: single diagonalization approach versus standard approaches, application to the methyl peroxy radical Ã←X̃ transition.

A new approach avoiding double (two-step) diagonalization is proposed to deal with internal rotation. The development of this method was stimulated by the jet-cooled high resolution spectrum of the vibrationless Ã←X̃ transition of the deuterated species of the methyl peroxy radical. This spectrum, originally analyzed with a rigid rotor Hamiltonian including spin-rotation but neglecting internal rotation, has been revisited in the previous paper (P.

Axis-switching in the vibrationless Ã←X̃ transition of the jet-cooled deuterated methyl peroxy radical CD3O2.

The jet-cooled high resolution spectrum of the vibrationless Ã←X̃ transition of the deuterated species of the methyl peroxy radical has been recently published in this journal (S. Wu, P. Dupré, P.

The vibrationless A<--X transition of the jet-cooled deuterated methyl peroxy radical CD3O2 by cavity ringdown spectroscopy.

The nearly rotationally resolved spectrum of the A (2)A(')<--X (2)A(") 0(0)(0) transition of perdeutero methyl peroxy near 1.35 microm has been studied via pulsed cavity ringdown spectroscopy. Albeit, this is a weak transition, it is possible to observe the spectrum under jet-cooled conditions (approximately 15 K) by combining a source of narrow-bandwidth radiation (approximately 250 MHz) with a supersonic slit-jet expansion incorporating an electric discharge.

Quasi-Fourier-transform limited, scannable, high energy titanium-sapphire laser source for high resolution spectroscopy.

A tunable injection seeded Ti:sapphire laser source has been developed and tested. Slave-master tandem cavity and ramp-lock-and-fire concepts have been implemented and fully controlled by a digital signal processor. A Fourier-transform-based analysis, as well as direct measurements, have demonstrated spectral linewidths in the range of 3.

High-resolution IR cavity ring-down spectroscopy of jet-cooled free radicals and other species.

Initial spectral results are reported from a newly constructed cavity ringdown spectrometer. The apparatus incorporates a slit-jet expansion, with or without a discharge, to produce cold sample molecules. High spectral resolution in both the near- and mid-IR is obtained by using stimulated Raman scattering of the pulsed amplified output of a cw Ti:Sa ring laser.

Continuous-wave cavity ringdown spectroscopy of the 8nu polyad of water in the 25,195-25,340 cm(-1) range.

State-of-the-art experiments and calculations are used to record and assign the data obtained in the weakly absorbing blue energy region of the H2O spectrum. Continuous-wave cavity ringdown absorption spectroscopy with Doppler resolution is used to probe the range from 25,195 to 25,470 cm(-1) with an absorption sensitivity of approximately 1 parts per 10(9) (ppb)/cm. 62 lines of the polyad nu(OH)=8 are reported, of which 43 are assigned using variational nuclear calculations.

Jet-cooled laser spectroscopy of the cyclohexoxy radical.

The laser-induced fluorescence and laser-excited dispersed fluorescence spectra of the cyclohexoxy radical has been observed under two sets of free-jet-cooling conditions, characterized by rotational temperatures of approximately 1 and 100 K. Although five conformers of cyclohexoxy are possible, it appears that all presently observed spectral bands can be accounted for by a single one. All cold spectral bands are assigned to the B-X electronic transition of the cyclohexoxy radical.