Presentation is loading. Please wait.

Presentation is loading. Please wait.

1 Laboratoire de Spectrométrie Physique (CNRS UMR C5588) Université Joseph Fourier de Grenoble (France) M. Chenevier, F.

Similar presentations


Presentation on theme: "1 Laboratoire de Spectrométrie Physique (CNRS UMR C5588) Université Joseph Fourier de Grenoble (France) M. Chenevier, F."— Presentation transcript:

1 1 Laboratoire de Spectrométrie Physique (CNRS UMR C5588) Université Joseph Fourier de Grenoble (France) M. Chenevier, F. Stoeckel, A. Kachanov and D. Romanini IntraCavity Laser Absorption Spectroscopy

2 2 Introduction: High Sensitive Absorption Techniques  increase of l : multipass cell, ICLAS, CRDS  decrease of the noise level : in particular FMDL and also CRDS, OA  measurement of the absorbed energy dark background methods: OA and OT NB. If the absorption linewidth is limited by the instrumental resolution, sensitivity  when the spectral resolution 

3 3 absorber l  v Principles of Intracavity Laser Absorption Spectroscopy emission spectrum I laser cavity L mirror Є laser gain with c: speed of light, t g : generation time L eq = c t g l / L

4 4 Principles of Intracavity Laser Absorption Spectroscopy

5 5 Spectral dynamics of ICLAS I (v, t g ) = e -  L eq 300 µs  90 km  min ~ cm -1 L eq = c t g l / L

6 6

7 7 ICLAS spectrum of 12 C 2 H 2 presenting the Q branch of the  -  band at cm -1. P= 15 Torr (20 hPa) and l eq = 8.6 km.

8 8 ICLAS set up ICLAS set up

9 9 Two times ICLAS (A. Kachanov, D. Romanini, A. Charvat, and B. Abel (1998) 4000 spectral elements recorded within 0.5ms!!!

10 10 Correction of the Atmospheric Absorption Background

11 11 Detection and measurement of low concentrated species Detection of forbidden transitions Line profile analysis  (  k  

12 12 ICLAS-dye of HDO

13 13 ICLAS- VECSEL of H2O Comparison with current databases

14 14 ICLAS is a quantitative method Comparison ICLAS-FTS (Kalmar and O’Brien JMS 192, (1998) Line Position (cm-1) Intensity in units of cm -2 /atm at 300K Absorbance vs Generation Time Absorbance vs Pressure FTS and Multipass (Toth et al)

15 15 ICLAS of weak vibronic transition jet cooled NO 2 in the near infrared

16 16 Plasma Diagnostics:Absolute Density and Temperature measurements of N 2 (A 3  u + ) in a microwave discharge

17 Medium Resolution High resolution Cooled cell (77K) Transmission ) H2OH2O Wavenumber (cm Supersonic expansion (O 2 ) 2 Cell cooled down to 77K First observation of the (O 2 ) 2 dimer of oxygen (1-0) band at 598 nm First observation of the (O 2 ) 2 dimer of oxygen (1-0) band at 598 nm [O 2 ( 1  g ) (v=0)+ O 2 ( 1  g ) ( v=1 ) ][O 2 ( 3  g ) (v=0) ] 2 Cooled cell

18 18 l/L~50%  t=50 min l/L~5%  t ~ 10 sec p = 2.7 bar (continuous expansion) p = 9 bar Comparison: ICLAS and CRDS of the (0-0) band of (O 2 ) 2 [O 2 ( 1  g ) (v=0)+ O 2 ( 1  g ) ( v=0 ) ][O 2 ( 3  g ) (v=0) ] 2

19 19 Spectral regions accessible for ICLAS Ti:Sa Nd:glass VECSEL cm -1 dyes V CH V SiH

20 20 VeCSEL - Vertical External Cavity Surface Emitting Laser Photoluminescence of a VeCSEL sample VeCSEL laser structure

21 21 ICLAS + VeCSEL AOM CM Diode Laser OC CCD Spectrograph M Inj MQW s PD Oscilloscope tgtg tgtg Peltier Intracavity Cell

22 22 Head of VeCSEL MQWs SDL - diode pumping laser Intracavity cell Concave mirror Cooling Peltier element Towards the output mirror and spectrometer

23 23 ICLAS + VeCSEL at 1.1  m

24 24 ICLAS_VECSEL of H 2 S in the region of the (40 ±, 0) transition ICLAS-VECSEL P=27 Torr l eq =30km

25 25 Specific laser dynamics of a VECSEL: spectral condensation Spectral condensation increases with:  Gas pressure  Line intensity  Pumping rate  Generation time Dependence on the gas pressure

26 26 Advantages of ICLAS Quantitative accuracy similar to classical absorption Not fluorescing transitions Limited quantity of gas required (typically 1mmol) Possible association with slit jet or reactor MULTIPLEX ADVANTAGE Near infrared and visible accessible Drawbacks of ICLAS Need for a reference for wavenumber calibration Spectral resolution limited by the spectrograph Baseline uncertainty in the case of broad unresolved spectrum UV not accessible Summary


Download ppt "1 Laboratoire de Spectrométrie Physique (CNRS UMR C5588) Université Joseph Fourier de Grenoble (France) M. Chenevier, F."

Similar presentations


Ads by Google