Interference-based remote raman spectroscopy enhancement method

Abstract

This invention discloses a long-range Raman spectroscopy enhancement method based on mutual interference. The method includes: irradiating a mixed gas sample of CO2 and N2 with a 355nm working laser and a 342nm ultraviolet laser simultaneously, so that a 2307cm² Raman spectroscopy enhancement is generated under the 342nm ultraviolet laser irradiation. ‑1 The characteristic Raman peak of N2 and the 1285 cm⁻¹ generated by the 355 nm working laser. ‑1 The characteristic Raman peaks of CO2 coincide, thus forming resonance or interference enhancement; or, a mixture of CO2 and N2 gas samples is irradiated with both a 355nm working laser and a 685nm infrared laser, resulting in a 2307cm² peak generated under 685nm infrared laser irradiation. ‑1 The characteristic Raman peak of N2 and the 1285 cm⁻¹ generated by the 355 nm working laser. ‑1 The frequency difference between the characteristic Raman peaks of CO2 is exactly equal to their frequency, thus promoting or inducing enhancement. A background subtraction scheme is used to suppress crosstalk Raman spectra generated by 342nm ultraviolet laser or 685nm infrared laser, obtaining accurate Raman spectra and achieving cross-interference enhancement of long-range Raman spectra. This invention makes long-distance detection of CO2 in the atmosphere relatively easy.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of Fourier transform Raman spectrum analysis, and in particular to a remote Raman spectrum enhancement method based on mutual interference. BACKGROUND

[0002] CO2 is the most important greenhouse gas causing global warming, and Raman spectrum has high accuracy, high sensitivity and high reliability, and is an ideal monitoring method for atmospheric CO2.

[0003] In the process of implementing the technical method of the embodiments of the present application, the present application inventors have found at least the following technical problems in the prior art:

[0004] Because the Raman scattering cross-section is small, and the concentration of CO2 gas in the atmosphere is very low, it is difficult to effectively obtain the remote Raman spectrum signal of atmospheric CO2, and it is difficult to detect remotely.

[0005] In summary, the existing remote Raman spectrum enhancement method has great difficulty in remotely detecting CO2 gas in the atmosphere. SUMMARY

[0006] The embodiments of the present application provide a remote Raman spectrum enhancement method based on mutual interference, which solves the technical problem of great difficulty in remotely detecting CO2 gas in the atmosphere by the existing remote Raman spectrum enhancement method.

[0007] The embodiments of the present application provide a remote Raman spectrum enhancement method based on mutual interference, which comprises: irradiating a mixed gas sample of CO2 and N2 with 355nm working laser and 342nm ultraviolet laser, so that the 2307cm -1 N2 characteristic Raman peak generated under the irradiation of the 342nm ultraviolet laser coincides with the 1285cm -1 CO2 characteristic Raman peak generated by the 355nm working laser, thereby forming resonance or interference enhancement; or irradiating a mixed gas sample of CO2 and N2 with 355nm working laser and 685nm infrared laser, so that the 2307cm -1 N2 characteristic Raman peak generated under the irradiation of the 685nm infrared laser coincides with the 1285cm -1 CO2 characteristic Raman peak generated by the 355nm working laser, and the frequency difference between them is exactly equal to its frequency, thereby forming promotion or induction enhancement; a background subtraction scheme is adopted to suppress the crosstalk Raman spectrum generated by the 342nm ultraviolet laser or the 685nm infrared laser, to obtain accurate Raman spectrum, and realize mutual interference enhancement of remote Raman spectrum.

[0008] Optionally, the 2307cm -1N2 characteristic Raman peak and the 1285 cm -1 CO2 characteristic Raman peak coincides, thereby forming resonance or interference enhancement, specifically including: 1285 cm -1 The wavelength λ1 of the characteristic Raman peak is: N2 characteristic Raman peak generated under the irradiation of the 342 nm ultraviolet laser is 2307 cm -1 The wavelength λ2 of the characteristic Raman peak is: The CO2 characteristic Raman peak generated by the 355 nm working laser and the N2 characteristic Raman peak generated by the 342 nm ultraviolet laser approximately coincide, thereby forming resonance or interference enhancement.

[0009] Optionally, the 2307 cm -1 N2 characteristic Raman peak and the 1285 cm -1 The frequency difference between the CO2 characteristic Raman peaks is exactly equal to its frequency, thereby forming promotion or induction enhancement, specifically including: 1285 cm -1 The frequency ω1 of the characteristic Raman peak is: Wherein c is the speed of light; N2 characteristic Raman peak generated under the irradiation of the 685 nm infrared laser is 2307 cm -1 The wavelength λ3 of the characteristic Raman peak is: 2307 cm -1 The frequency ω3 of the characteristic Raman peak is: The frequencies ω1, ω3 of the characteristic Raman peaks of CO2 and N2 and the 685 nm infrared laser satisfy the following relationship: The frequency difference between the CO2 characteristic Raman peak generated by the 355 nm working laser and the N2 characteristic Raman peak generated by the 685 nm infrared laser is approximately equal to the infrared laser frequency, thereby forming promotion or induction enhancement.

[0010] Optionally, the scheme of background subtraction is adopted to suppress the crosstalk Raman spectrum generated by the 342 nm ultraviolet laser or the 685 nm infrared laser, and accurate Raman spectrum is obtained, specifically including: measuring a single Raman spectrum generated by the introduced laser as a background, the introduced laser being the 342 nm ultraviolet laser or the 685 nm infrared laser; utilizing the simple superposition characteristics of the Raman spectrum, subtracting the background from the mixed Raman spectrum generated by the 355 nm working laser and the introduced laser to suppress the crosstalk Raman spectrum, and obtaining accurate Raman spectrum.

[0011] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0012] A long-range Raman spectroscopy enhancement method based on mutual interference, the method comprising: irradiating a mixed gas sample of CO2 and N2 with a 355 nm working laser and a 342 nm ultraviolet laser simultaneously, such that a 2307 cm⁻¹ spectral density is generated under the irradiation of the 342 nm ultraviolet laser. -1 The characteristic Raman peak of N2 and the 1285 cm⁻¹ generated by the 355 nm working laser. -1 The characteristic Raman peaks of CO2 coincide, thus forming resonance or interference enhancement; or a mixture of CO2 and N2 gas samples is irradiated with both a 355nm working laser and a 685nm infrared laser, resulting in a 2307cm² peak generated under the 685nm infrared laser irradiation. -1 The characteristic Raman peak of N2 and the 1285 cm⁻¹ generated by the 355 nm working laser. -1 The frequency difference between the characteristic Raman peaks of CO2 is exactly equal to its frequency, thus promoting or inducing enhancement. A background subtraction scheme is used to suppress crosstalk Raman spectra generated by the 342nm ultraviolet laser or the 685nm infrared laser, obtaining accurate Raman spectra and achieving cross-interference enhancement of long-range Raman spectra. Since the concentration of CO2 in the atmosphere is very low, but the concentration of N2 is very high, this invention utilizes the Raman scattering light of N2 to promote or even convert the Raman scattering light of CO2, which will greatly enhance the Raman spectral signal of CO2, making long-distance detection easier and effectively solving the technical problem of the difficulty in long-distance detection of atmospheric CO2 gas in existing long-range Raman spectral enhancement methods. Attached Figure Description

[0013] Figure 1 The flowcharts show two schemes for achieving remote Raman spectral interferometry enhancement in one embodiment of the present invention. Detailed Implementation

[0014] This invention provides a remote Raman spectroscopy enhancement method based on mutual interference, which solves the technical problem of the difficulty of detecting CO2 gas in the atmosphere at long distances using existing remote Raman spectroscopy enhancement methods.

[0015] like Figure 1 As shown, the long-range Raman spectral enhancement method based on mutual interference in this embodiment takes advantage of the low CO2 content but high N2 content in the atmosphere. It utilizes the Raman scattering light of N2 to promote or even convert the Raman scattering light of CO2, thereby enhancing the Raman spectral signal of CO2. The method includes the following steps:

[0016] A mixture of CO2 and N2 gas samples was irradiated simultaneously with a 355nm working laser and a 342nm ultraviolet laser, resulting in a 2307cm³ gas volume generated under the 342nm ultraviolet laser irradiation. -1 The characteristic Raman peak of N2 and the 1285 cm⁻¹ generated by the 355 nm working laser.-1 CO2 characteristic Raman peaks coincide, thus forming resonance or interference enhancement; or 355 nm working laser and 685 nm infrared laser are used to irradiate CO2 and N2 mixed gas sample, so that 2307 cm -1 N2 characteristic Raman peak and 1285 cm -1 The frequency difference between CO2 characteristic Raman peaks is exactly equal to its frequency, thus forming promotion or induction enhancement.

[0017] 2307 cm -1 N2 characteristic Raman peak and 1285 cm -1 CO2 characteristic Raman peaks coincide, thus forming resonance or interference enhancement, specifically including:

[0018] CO2 characteristic Raman peak generated by 355 nm working laser and 1285 cm -1 The wavelength λ1 of the characteristic Raman peak is:

[0019]

[0020] 2307 cm -1 The wavelength λ2 of the characteristic Raman peak is:

[0021]

[0022] CO2 characteristic Raman peak generated by 355 nm working laser and N2 characteristic Raman peak generated by 342 nm ultraviolet laser approximately coincide, thus forming resonance or interference enhancement.

[0023] 2307 cm -1 N2 characteristic Raman peak and 1285 cm -1 The frequency difference between CO2 characteristic Raman peaks is exactly equal to its frequency, thus forming promotion or induction enhancement, specifically including:

[0024] CO2 characteristic Raman peak generated by 355 nm working laser and 1285 cm -1 The frequency ω1 of the characteristic Raman peak is:

[0025]

[0026] Where c is the speed of light;

[0027] 2307 cm -1 The wavelength λ3 of the characteristic Raman peak is:

[0028]

[0029] 2307cm -1 The frequency ω3 of the characteristic Raman peak is:

[0030]

[0031] The frequencies ω1, ω3 of the characteristic Raman peaks of CO2 and N2 satisfy the following relationship with the 685nm infrared laser:

[0032]

[0033] The frequency difference between the characteristic Raman peak of CO2 generated by the 355nm working laser and the characteristic Raman peak of N2 generated by the 685nm infrared laser is approximately equal to the frequency of the infrared laser, thereby forming promotion or induction enhancement.

[0034] The present application utilizes the simple superposition property of Raman spectrum to subtract the single Raman spectrum generated by the introduced laser from the mixed spectrum. The present application adopts the background subtraction scheme to suppress the crosstalk Raman spectrum generated by the 342nm ultraviolet laser or the 685nm infrared laser, and obtains an accurate Raman spectrum, which specifically comprises:

[0035] A single Raman spectrum generated by the introduced laser is measured as a background, and the introduced laser is the 342nm ultraviolet laser or the 685nm infrared laser;

[0036] The simple superposition property of Raman spectrum is utilized to subtract the background from the mixed Raman spectrum generated by the 355nm working laser and the introduced laser to suppress the crosstalk Raman spectrum, and an accurate Raman spectrum is obtained.

[0037] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application belong to the scope of the claims of the present application and the equivalent technologies thereof, the present application also intends to include these modifications and variations.

Claims

1. A long-range Raman spectral enhancement method based on mutual interference, characterized in that, The method includes: A mixture of CO2 and N2 gas samples was irradiated simultaneously with a 355nm working laser and a 342nm ultraviolet laser, resulting in a 2307 cm⁻¹ gas concentration generated under the 342nm ultraviolet laser irradiation. -1 The characteristic Raman peak of N2 and the 1285 cm⁻¹ generated by the 355 nm working laser. -1 The characteristic Raman peaks of CO2 coincide, thus forming resonance or interference enhancement; or a mixture of CO2 and N2 gas samples is irradiated with both a 355nm working laser and a 685nm infrared laser, resulting in a 2307 cm⁻¹ peak generated under the 685nm infrared laser irradiation. -1 The characteristic Raman peak of N2 and the 1285 cm⁻¹ generated by the 355 nm working laser. -1 The frequency difference between the characteristic Raman peaks of CO2 is exactly equal to its frequency, thus promoting or inducing enhancement. A background subtraction scheme is used to suppress crosstalk Raman spectra generated by the 342nm ultraviolet laser or the 685nm infrared laser, thereby obtaining accurate Raman spectra and achieving cross-interference enhancement of long-range Raman spectra. The background subtraction scheme suppresses crosstalk Raman spectra generated by the 342nm ultraviolet laser or the 685nm infrared laser to obtain accurate Raman spectra, specifically including: A single Raman spectrum generated solely by the introduced laser is measured as a background, wherein the introduced laser is either the 342 nm ultraviolet laser or the 685 nm infrared laser; By utilizing the simple superposition property of Raman spectra, the background is subtracted from the mixed Raman spectrum generated by the 355nm working laser and the introduced laser to suppress crosstalk Raman spectra and obtain accurate Raman spectra.

2. The method as described in claim 1, characterized in that, The 2307 cm generated under the 342nm ultraviolet laser irradiation -1 The characteristic Raman peak of N2 and the 1285 cm⁻¹ generated by the 355 nm working laser. -1 The characteristic Raman peaks of CO2 overlap, thus forming resonance or enhanced interference, specifically including: CO2 produced 1285 cm⁻¹ under irradiation by the 355nm working laser. -1 The wavelength λ1 of the characteristic Raman peak is: N2 produced 2307 cm⁻¹ under 342nm ultraviolet laser irradiation. -1 The wavelength λ2 of the characteristic Raman peak is: The characteristic Raman peak of CO2 generated by the 355nm working laser and the characteristic Raman peak of N2 generated by the 342nm ultraviolet laser approximately overlap, thus forming resonance or interference enhancement.

3. The method as described in claim 1, characterized in that, The 2307 cm generated under the 685nm infrared laser irradiation -1 The characteristic Raman peak of N2 and the 1285 cm⁻¹ generated by the 355 nm working laser. -1 The frequency difference between the characteristic Raman peaks of CO2 is exactly equal to their frequency, thus promoting or inducing enhancement, specifically including: CO2 produced 1285 cm⁻¹ under irradiation by the 355nm working laser. -1 The frequency ω1 of the characteristic Raman peak is: Where c is the speed of light; N2 produced 2307 cm under the irradiation of the 685nm infrared laser. -1 Wavelength of characteristic Raman peak for: 2307 cm -1 The frequency ω3 of the characteristic Raman peak is: The frequencies ω1 and ω3 of the characteristic Raman peaks of CO2 and N2 satisfy the following relationship with the 685nm infrared laser: The frequency difference between the CO2 characteristic Raman peak generated by the 355nm working laser and the N2 characteristic Raman peak generated by the 685nm infrared laser is approximately equal to the infrared laser frequency, thereby promoting or inducing enhancement.

Images