R. Bacis

New laser-induced fluorescence Fourier transform spectrometry: The 7Li2 ground-state dissociation limit

Abstract The use for the first time of a high-resolution Fourier transform spectrometer to analyse the laser-induced fluorescence from a ring dye laser allows o

Rotation–vibration analysis of the B 0+u–a 1g and B 0+u–a′ 0+g electronic systems of I2 by laser‐induced‐fluorescence Fourier‐transform spectroscopy

The spectrum of fluorescence excited by the 514.5 nm line of a multimode Ar+ laser is recorded by a Fourier‐transform spectrometer. In the region 7000–7300 cm−1 (1.43 to 1.37 μm), transitions from the B 0+u state are recorded into two states, which had been previously only indirectly observed, as well as into the X 1Σ+ state. Vibrational levels 0–9 for the 0+g and 0–14 for the 1g states are sampled. The principal molecular constants determined are as follows: where all constants are in cm−1 except when noted, with 2σ uncertainties in parentheses.

Rotationally resolved absorption spectrum of the O2 dimer in the visible range

Abstract The rotationally resolved absorption spectrum of two bands of the oxygen dimer near 630 and 578 nm have been recorded by intracavity laser absorption spectroscopy both in a supersonic slit expansion of pure O 2 and in a cell cooled at 77 K. These bands correspond to the transitions [ O 2 ( 1 Δ g ) v=0 ] 2 ←[ O 2 ( 3 Σ g − ) v=0 ] 2 and [ O 2 ( 1 Δ g ) v=0 – O 2 ( 1 Δ g ) v=1 ]←[ O 2 ( 3 Σ g − ) v=0 ] 2 . From the extension of the highly congested rotational structure, the dissociation energy of the ground and excited states are estimated to be 80 and 40 cm −1 , respectively. These values agree reasonably well with the results of ab initio calculations of the potential energy surface.

Structure and rovibrational analysis of the [O2(1Δg)v=0]2←[O2(3Σg−)v=0]2 transition of the O2 dimer

The rotationally resolved absorption spectrum of the O2 dimer involving the [O2(1Δg)v=0]2←[O2(3Σg−)v=0]2 transition has been recorded near 632.6 nm by continuous wave Cavity Ring Down Spectroscopy in a supersonic slit jet expansion of pure O2. A quadratic dependence of the absorption in the jet versus the stagnation pressure is observed. A rotational temperature of 12 K is derived from the (O2)2 rotational analysis. The high spectral resolution of the CW-CRDS measurements limited by the residual Doppler broadening in the jet and the low rotational temperature allow the first rotational analysis in this open-shell complex. The same spectrum was also recorded by Intracavity Laser Absorption Spectroscopy and the comparison of the performances of the two methods is discussed. Among more than 600 lines measured between 15 800 and 15 860 cm−1 from the CW-CRDS spectrum, 40 were assigned to the RP0, RQ0, and RR0 branches of two subbands associated with B1−←A1+ and A1+←B1− transitions between the ground and excite...

Long range behavior of the gerade states near the 2P3/2+ 2P3/2 iodine dissociation limit by laser‐induced‐fluorescence Fourier‐transform spectroscopy

The near infrared LIF–FTS spectra from the I2 B 0u+ state, excited by an argon ion laser and recorded by a high resolution Fourier‐transform spectrometer, contain information about perturbations between the gerade states converging to the I2→2I(2P3/2) dissociation limit. The observed perturbation interactions are sampled at internuclear distances near 5 A and are interpreted in a separated atom (I2=Ia+Ib; ψI2=φaφb; φa=‖ ja=3/2, ma〉) basis set. Near r=5 A the X 0g+ and a′ 0g+ states are found to have predominant ma=−mb=±1/2 and ma=−mb=±3/2 character, respectively, but with slight ‖m‖=1/2∼‖m‖=3/2 mixing. In this pure ‖m‖ basis, S=sa+sb and Jatomic=ja+jb are not well defined, but in the limit of complete ‖m‖=1/2∼‖m‖= 3/2 mixing, S and Jatomic are well defined. The behavior of three gerade states (X 0g+, a′ 0g+, a 1g) at large internuclear distance has been analyzed using the long range theory of LeRoy and Bernstein. The results are in fair agreement with theoretical predictions, and give a direct and precise...

High resolution and sub‐Doppler Fourier transform spectroscopy: Iodine molecular fluorescence excited by the 514.5 and 501.7 nm Ar+ laser lines

Fluorescence from the I2 B O+u state, excited by the 514.5 and 501.7 nm cw Ar+ laser lines, is recorded using a high resolution Fourier transform spectrometer. Spectra are obtained with both multimode (6 GHz) and single mode (<100 MHz) Ar+ lasers, the latter spectra exhibiting reduced Doppler width. B O+u−X 1Σ+g fluorescence is recorded at 1 mK precision for v″=10–100, eQq″ quadrupole constants are obtained (±5%) from measured linewidths, broadening of quasibound X 1Σ+g rotational levels above the rotationless X 1Σ+g dissociation limit is observed, and perturbations of X 1Σ+ v″⩾92 by two previously unobserved long range I2 molecular states are detected. These two states, 0+g and 1g, which dissociate into two 2P3/2 I atoms, are also observed directly in the fluorescence spectrum. This paper presents illustrative examples; constants and a complete analysis will appear subsequently.

The chemical oxygen‐iodine laser: Comparison of a theoretical model with experimental results

The experimental performance of a small‐scale chemical oxygen‐iodine laser is compared to a theoretical model. Measuring the consumption of O2 (1Δg) in the region of the flame indicates that less than five molecules of O2 (1Δg) are required to dissociate one I2 molecule. It is shown that the hyperfine relaxation rates in the iodine atom increase both the laser threshold and the active transverse length of the cavity.

Hyperfine structure of higher rovibrational levels in the iodine B state studied by Ar+ laser induced fluorescence

Abstract The hyperfine structure of higher rovibrational levels in the iodine B state has been investigated by studying the fluorescence of a well collimated iodine molecular beam excited by the 5017 A Ar + laser line. Nine transitions: R(13) 61-0, P(12) 61-0, R(49) 67-0, R(39) 64-0, R(26) 62-0, P(56) 73-0, R(54) 70-0, R(55) 77-1, R(51) 68-0 were identified and their center of gravity located to an accuracy of ±0.001 cm -1 . A fit of the theoretically predicted hyperfine patterns to the observed spectra enables one to study the variation of the magnetic hyperfine constant C ′ with the vibrational quantum number υ′ in the range 61 ⩽ υ′ ⩽ 73. The observed behavior is well accounted for by a simple theoretical model developed by Vigue et al.

Comparison of emission spectra of CuCl2 obtained via energy transfer from O2(1Δg) with laser-induced fluorescence spectra

Abstract Red and infrared (≈8000 cm −1 ) emission was recorded from a flame produced by Cl 2 and O 2 ( 1 Δ g ) in the presence of hot copper, and from CuCl 2 excited directly by O 2 ( 1 Δ g ). We note similarities between these spectra and an infrared absorption spectrum of CuCl 2 . Laser-induced fluorescence spectra of CuCl 2 ( 2 Π− 2 Π g ) were excited using the red lines of a krypton-ion laser, and recorded at high resolution on a Fourier-transform spectrometer. A preliminary analysis of the series of rotational doublets observed gives T e ≈15800 cm −1 for the 2 Π u state and a well depth for 2 Π g greater than 4300 cm −1 .

Study of isotope effects in the ground state of the symmetrical isotopomers of CuCl2

Abstract Investigations of the ground state of CuCl 2 have been pursued, recording laser induced fluorescence spectra on a Bomem DA3 Fourier transform spectrometer in the range 10000–16500 cm −1 . A single mode ring dye laser, set in the red (615–665 nm), excited the 2 Π u - X 2 Π g electronic transition in copper dichloride vapour. Analysis of spectra recorded from isotopically enriched samples of CuCl 2 allowed us to check our assignment of vibrational stretching quantum numbers v 1 (⩽7) and v 3 (⩽8) in the ground state. A normal model including isotope effects has been used to fit data from all four symmetrical isotopomers of copper dichloride. The rms deviation of the fit containing about 4000 lines is 0.040 cm −1 . From this model, we find an equilibrium CuCl bond length of 0.203335(5) nm and force constant k 1 =277.28(1) N m −1 .