Communication: overtone (2NH) spectroscopy of NH3-Ar.

The Π (1(1)) ← Σ (0(0)) 2NH (ν1+ν3) band of the NH3-Ar van der Waals complex formed in a supersonic jet expansion, with origin at 6628 cm(-1) was recorded at high-resolution using cavity ring down spectroscopy. The analysis leads to upper state rotational constants and J-dependent predissociation lifetimes estimated from linewidth analysis, with a mean value about 0.6 ns.

High resolution spectroscopy of the Ar-D2O and Ar-HDO molecular complexes in the near-infrared range.

Three rovibrational bands of Ar-D2O and two rovibrational bands of Ar-HDO were observed in the 1.5 μm range by continuous wave cavity ringdown spectroscopy. Their analyses led to the determination of rotational constants for the upper states and vibrational shifts indicating that the potential energy surface is only slightly affected by the vibrational excitation.

High resolution overtone spectroscopy of the acetylene van der Waals dimer, ((12)C2H2)2.

CW-cavity ring down spectroscopy was used to record in a free jet expansion the spectrum of the absorption band in ((12)C(2)H(2))(2) with origin at 6547.6 cm(-1). It is a perpendicular band and corresponds to 2CH excitation in the hat unit of the T-shaped dimer.

High resolution spectroscopic investigation of a new van der Waals complex: C(2)H(2)-Kr.

The first observation in the near infrared of the (12)C(2)H(2)-Kr van der Waals complex is reported, leading to the determination of rotational constants and the prediction of the 1 0 1 (J'K(a)'K(c)') ← 0 0 0 (J''K(a)''K(c)'') microwave transition occurring at 3.334(4) MHz, useful for astrophysical detection.

Demonstration of cavity enhanced FTIR spectroscopy using a femtosecond laser absorption source.

A proof of principle experiment was performed by recording the cavity enhanced absorption spectrum of the weak b-X transition of molecular oxygen in the atmosphere using a Ti:Sa femtosecond laser as an absorption source and a high resolution continuous scan Fourier transform interferometer. The cavity was mode matched and either continuously scanned or stabilized at the so-called magic point. An optimal rms noise equivalent absorption of 3x10(-7) cm(-1) Hz(-1/2) was reached in the latter case, corresponding to alpha(min)=3x10(-7) cm(-1).

Investigation of the C2H2-CO2 van der Waals complex in the overtone range using cw cavity ring-down spectroscopy.

A slit nozzle supersonic expansion containing acetylene [492 SCCM (SCCM denotes cubic centimeter per minute at STP)] and carbon dioxide (740 SCCM) seeded into Ar (837 SCCM) is investigated using cw-cavity ring-down spectroscopy, in the 1.5 microm range. The C(2)H(2)-CO(2) van der Waals complex is observed around the nu(1) + nu(3) acetylenic band.

(12)C2H2-Ar van der Waals complex.

New theoretical and experimental results on the acetylene-Ar van der Waals complex are presented and the literature is reviewed. New ab initio calculations at the MP2 level were performed using large basis sets with diffuse functions and taking into account the basis set superposition error. It was found that the structure of acetylene is not significantly altered by the complexation and that its vibrational frequencies are only slightly lowered.

Absolute line intensities for formic acid and dissociation constant of the dimer.

Absolute line intensities in the nu(6) and nu(8) interacting bands of trans-HCOOH, observed near 1105.4 and 1033.5 cm(-1), respectively, and the dissociation constant of the formic acid dimer (HCOOH)(2) have been measured using Fourier transform spectroscopy at a resolution of 0.