Laser absorption spectroscopy isotopic gas analyzer

1. A gas analyzer system for measuring an isotopic ratio of a gaseous chemical species by an optical absorption spectroscopy method, the system comprises: an optical cavity containing a gas with the chemical species to be measured; a laser optically coupled to an optical cavity; a detector system for measuring absorption of laser light by the gas; and an intelligence module comprising a processor adapted to determine a concentration ratio of two different isotopologues, wherein rotational-vibrational spectra of the chemical species are measured at least within two non-overlapping spectral intervals separated by a minimum of 50 nm between any two spectral points from each of the spectral intervals and selected in such a way that a first rotational-vibrational line of a first rotational-vibrational band of a less abundant isotopologue is located in a first spectral interval, and a second rotational-vibrational line of a second rotational-vibrational band of a more abundant isotopologue is located in a second spectral interval, and a line intensity of the strongest line of the first rotational-vibrational band of the less abundant isotopologue is two or more times stronger than a line intensity of the strongest line of the second rotational-vibrational band of the more abundant isotopologue, and a ratio of an absorption spectrum of the less abundant isotopologue to the sum of absorption spectra of all other isotopologues of the chemical species weighted by mole-fraction abundance figures exceeds two somewhere in the first spectral interval, and a ratio of an absorption spectrum of the more abundant isotopologue to the sum of absorption spectra of all other isotopologues of the chemical species weighted by mole-fraction abundance figures exceeds two somewhere in the second spectral interval.

2. The system of claim 1 , wherein the pressure broadening coefficients of the first line and the second line are different by no more than 50%.

3. The system of claim 1 , wherein the temperature dependence coefficients of the first line and the second line are different by no more than 50%.

4. The system of claim 1 , wherein the optical absorption spectroscopy method comprising of at least one of the following methods: the cavity ring down spectroscopy method, the cavity enhanced absorption spectroscopy method, the cavity phase shift spectroscopy method, the integrated cavity output spectroscopy method, or the cavity enhanced photo-acoustic spectroscopy method.

5. The system of claim 1 , wherein the optical cavity is a resonant optical cavity.

6. The system of claim 1 , wherein the detector system includes one of a photo-detector configured to measure an intensity of the intra-cavity light or both a photo-acoustic sensor configured to measure photo-acoustic waves generated in the cavity and a photo-detector configured to measure an intensity of the intra-cavity light.

7. The system of claim 1 , wherein one of the measured isotopologues is 16 O 13 C 16 O and another measured isotopologue is 16 O 12 C 16 O.

8. The system of claim 1 , further comprising a temperature sensor for measuring a temperature of the gas in the optical cavity; and a pressure sensor for measuring a pressure of the gas in the optical cavity.

9. The system of claim 8 , further comprising a temperature control element configured to control a temperature of the gas in the optical cavity and a pressure control element configured to control a pressure of the gas in the optical cavity.

10. A gas analyzer system for measuring an isotopic ratio of a gaseous chemical species by an optical absorption spectroscopy method, the system comprises: an optical cell containing a gas with the chemical species to be measured; a laser configured to emit light into an optical cell; a detector system for measuring absorption of laser light by the gas; and an intelligence module comprising a processor adapted to determine a concentration ratio of two different isotopologues, wherein rotational-vibrational spectra of the chemical species are measured at least within two non-overlapping spectral intervals separated by a minimum of 50 nm between any two spectral points from each of the spectral intervals and selected in such a way that a first rotational-vibrational line of a first rotational-vibrational band of a less abundant isotopologue is located in a first spectral interval, and a second rotational-vibrational lines of a second rotational-vibrational band of a more abundant isotopologue is located in a second spectral interval, and a line intensity of the strongest line of the first rotational-vibrational band of the less abundant isotopologue is two or more times stronger than a line intensity of the strongest line of the second rotational-vibrational band of the more abundant isotopologue, and a ratio of an absorption spectrum of the less abundant isotopologue to the sum of absorption spectra of all other isotopologues of the chemical species weighted by mole-fraction abundance figures exceeds two somewhere in the first spectral interval, and a ratio of an absorption spectrum of the more abundant isotopologue to the sum of absorption spectra of all other isotopologues of the chemical species weighted by mole-fraction abundance figures exceeds two somewhere in the second spectral interval.

11. A method of measuring an isotopic ratio of a gaseous chemical species, the method comprising: coupling laser light to an optical cavity containing a gas with the chemical species to be measured; measuring an absorption of the laser light by the gas; determining the concentration ratio of two different isotopologues, wherein rotational-vibrational spectra of the chemical species are measured at least within two non-overlapping spectral intervals separated by a minimum of 50 nm between any two spectral points from each of the spectral intervals and selected in such way that a first rotational-vibrational line of a first rotational-vibrational band of a less abundant isotopologue is located in a first spectral interval, and a second rotational-vibrational line of a second rotational-vibrational band of a more abundant isotopologue is located in a second spectral interval, and a line intensity of the strongest line of the first rotational-vibrational band of the less abundant isotopologue is two or more times stronger than a line intensity of the strongest line of the second rotational-vibrational band of the more abundant isotopologue, and a ratio of an absorption spectrum of the less abundant isotopologue to the sum of absorption spectra of all other isotopologues of the chemical species weighted by mole-fraction abundance figures exceeds two somewhere in the first spectral interval, and a ratio of an absorption spectrum of the more abundant isotopologue to the sum of absorption spectra of all other isotopoloques of the chemical species weighted by mole-fraction abundance figures exceeds two somewhere in the second spectral interval.

12. The method of claim 11 , wherein the pressure broadening coefficients of the first line and the second line are different by no more than 50%.

13. The method of claim 11 , wherein the temperature dependence coefficients of the first line and the second line are different by no more than 50%.

14. The method of claim 11 , wherein the optical absorption spectroscopy method comprising at least one of the following methods: the cavity ring down spectroscopy method, the cavity enhanced absorption spectroscopy method, the cavity phase shift spectroscopy method, the integrated cavity output spectroscopy method, or the cavity enhanced photo-acoustic spectroscopy method.

15. The method of claim 11 , wherein the optical cavity is a resonant optical cavity.

16. The method of claim 11 , wherein one of the measured isotopologues is 13 C 16 O 2 and another measured isotopologue is 12 C 16 O 2 .

17. The method of claim 11 , further comprising: measuring a temperature of the gas in the optical cavity by a temperature sensor and measuring a pressure of the gas in the optical cavity by a pressure sensor.

18. The method of claim 17 , further comprising: controlling a temperature of the gas in the optical cavity by a temperature control element and controlling a pressure of the gas in the optical cavity by a pressure control element.