arXiv subjects

Guy Guelachvili

Publications and source records attributed to Guy Guelachvili.

21 records · Page 2Linked to original sources

arXiv2006

Acetylene weak bands at 2.5 $μ$m from intracavity Cr2+:ZnSe laser absorption observed with time-resolved Fourier transform spectroscopy

The spectral dynamics of a mid-infrared multimode Cr^2+:ZnSe laser located in a vacuum sealed chamber containing acetylene at low pressure is analyzed by a stepping-mode high-resolution time-resolved Fourier transform interferometer. Doppler-limited absorption spectra of C_2H_2 in natural isotopic abundance are recorded around 4000 cm^-1 with kilometric absorption path lengths and sensitivities better than 3 10^-8 cm-1. Two cold bands are newly identified and assigned to the n_1+n_4^1 and n_3+n_5^1 transitions of ^12C^13CH_2. The n_1+n_5^1 band of ^12C_2HD and fourteen ^12C_2H_2 bands are observed, among which for the first time n_2+2n_4^2+n_5^-1.

physics.chem-ph↗

arXiv2006

Cation-like Doppler shifts from a neutral molecule in an electrical discharge

Velocity-modulation Fourier transform emission spectra from a N_2O/He discharge plasma recorded between 1 and 5.5 $μ$m are described. Surprisingly, they show Doppler-shifted lines for the E ^2 Σ^+ - D ^2 Σ^+, C ^2 Π- A ^2 Σ^+, and D ^2 Σ^+ - A ^2 Σ^+ Rydberg-Rydberg rovibronic transitions of the nitric oxide neutral molecule. These polarity-dependent Doppler-shifts are those of positively charged particles. Vibration-rotation lines of NO and transitions from other neutral molecules like N_2 are also present in the spectra with comparable intensities and remain unshifted. Experimental investigations and possible explanations are discussed.

physics.chem-ph↗

arXiv2006

Time-resolved Fourier transform intracavity spectroscopy with a Cr2+:ZnSe laser

Intracavity laser absorption spectroscopy (ICLAS) with an evacuated Cr2+: ZnSe laser is performed with a high-resolution time-resolved Fourier transform interferometer with a minimum detectable absorption coefficient equal to 4 10-9 cm-1 Hz-1/2 in the 2.5$μ$m region. This represents the extreme limit presently reached in the infrared by ICLAS with Doppler limited resolution. The broad gain band of the crystal allows a spectral coverage at most equal to 125 nm, wide enough to see entire vibration bands. Weak CO2 bands observed up to now only in the Venus atmosphere are recorded for the first time in a laboratory. H2O detection limit down to 0.9 ppbv is also demonstrated.

physics.optics↗