Precise wave-number calibration in molecular spectra: the case of Ti 

Abstract

The spectrum of the titaniu m monoxide molecule has been studied by means of a sub-D oppler experiment combining an effusive beam of TiO and a cw tunable dye laser beam. In the 560 nm to 565 nm range, 260 absorption lines have been recorded through the laser-induced ¯uorescence technique of detection. Because the absorption pro® les are narrow, a sensitiv e program of data acquisition and analysis is used. These wave-numbers have been measured by reference to the absorption spectrum of the iodine molecule to an absolute uncertainty of 30 MHz (0,001 cm ±1 ). For the 140 lines of the c 1 -a 1 (0-0) band of 48 Ti 16 O which have been identi® ed, the rm s error between m easured and calculated wave-numbers is just 21 MHz (0,0007 cm ±1 ).

Isotope Shifts in the TiO B–X (1–0) Band

“…The accurate calibration of the laser frequency scale is achieved by simultaneously recording the absorption spectrum of iodine molecules (32) and reference fringes-750 MHz apart-provided by a spherical Fabry-Perot etalon. Owing to a semi-automatic calibration program (33) intense absorption lines can be positioned to an accuracy of 1-2 10 −3 cm −1 . This system of detection is quasilinear with isotope abundance, in spite of weak saturation effects with laser fluence.…”

The TiOc1Φ–a1Δ (0–0) Band at Sub-Doppler Spectral Resolution: Spin–Orbit Interactions in thecState

“…A weight ratio of 50/ systematically measured by reference to several close I 2 1 was applied to our data, in relation with the experimental lines, the internal coherence of the determination varying wavenumbers accuracy of the three sets. from 0.2 to 1 1 10 03 cm 01 (28). More specifically, the following transitions were taken Under the above experimental conditions, the spectrum into account: shows essentially 48 Ti 16 O lines belonging to the (0-0) band, several lines belonging to the (1-1) band (head for…”

High Resolution Spectroscopy With Molecular Beams and Tunable Lasers

“…and 2). To control the regularity of the frequency scale and to determine absolute TiO wavenumbers, the absorption spectrum of the iodine molecule and interference fringes provided by a Fabry-Perot etalon are simultaneously recorded and treated by numerical techniques [15].…”

“…Therefore, a more intense laser beam was used, with a slight saturation of the absorption and a weak broadening of the profiles. Owing to the recent numerical treatment of the laser frequency scale [15] the accuracy of wavenumber measurements could be reduced to 10-3 cm-1 for 130 lines of 48TIO measured in the range 17,700 17,860 cmand the rotational analysis could be conducted up to J 96. The spectroscopic data were reduced to a set of 11 effective molecular constants with a standard deviation of 0.7 10 -3 cm -1 between measured and fi, tted wavenumbers, to compare with 20 10 -3 cm -1 obtained in an older analysis performed with a Doppler-limited light source [21].…”