The present disclosure relates generally to Rydberg fingerprint spectroscopy and, more specifically, to chemical sensing in multi-component mixtures, like gaseous mixtures, using multi-dimensional Rydberg fingerprint spectroscopy.
The analysis of gaseous mixtures is of great practical importance in many areas, including medicine, environmental science, industrial processes, and the like. Hydrogen sulfide (H2S) is an example of a gas that may be important to detect in some circumstances, like oil drilling. Natural oil deposits deep underground are highly pressurized and may include significant amounts of dissolved H2S. When the oil is pumped to the surface, the pressure on the natural oil deposit can decrease, causing the H2S gas to escape. Consequently, oil rig workers are potentially unknowingly exposed to harmful levels of H2S. While the human nose is quite sensitive to H2S, the human nose can become saturated and unable to detect the smell of H2S after prolonged exposure, preventing oil rig workers from smelling dangerous levels of H2S. A sensitive and real-time detector capable of monitoring the air surrounding an oil well or platform is needed to protect oil workers and ensure that their exposure to dangerous gases, such as H2S, remains below critical levels.
Traditional approaches to analyze gaseous mixtures for dangerous gasses include mass spectrometry, gas chromatography, ion mobility spectrometry, infrared spectroscopy, hyperspectral imaging, or the like. However, these traditional approaches lack one or more of the following: sensitivity, chemical specificity, generality, ability to discern components in the presence of other components, and/or operational speed and convenience. Additionally, while Rydberg Fingerprint Spectroscopy has been proven to show optical transitions that are very specific to probed molecules, Rydberg Fingerprint Spectroscopy has not been able to analyze gaseous mixtures or other multi-component mixtures due to associated difficulties.
The present disclosure improves traditional Rydberg Fingerprint Spectroscopy by increasing its associated dimensionality. Accordingly, multi-dimensional Rydberg Frequency Spectroscopy can be used to perform chemical sensing to detect and identify components of multi-component mixtures (such as gaseous mixtures). The systems and methods enable the real-time detection of chemicals in substantial air volumes in natural environments with high sensitivity.
A system is described that uses multidimensional Rydberg Fingerprint Spectroscopy to perform chemical sensing to detect and identify components of gaseous mixtures (a sample). The system includes at least a tunable pulsed excitation laser; a tunable pulsed transition laser; and an ionization or light absorption detector. A pulsed laser beam having a first wavelength can be delivered to a sample using the tunable pulsed excitation laser; and a pulsed laser beam having a second wavelength can be delivered to the sample point using the tunable pulsed transition laser. The pulsed laser beam having the first wavelength and the pulsed laser beam having the second wavelength have energy sufficient to excite an electron of a sample molecule to a Rydberg state. A level of ionization or light absorption can be detected at the sample point by the ionization or light absorption detector. The level of ionization or light absorption detected and the first and second wavelengths are used to determine the presence and identity of one or more chemicals in the sample.
A method is described that uses multidimensional Rydberg Fingerprint Spectroscopy to perform chemical sensing to detect and identify components of gaseous mixtures (a sample). The method includes delivering a pulsed laser beam having a first wavelength to a sample using a tunable pulsed excitation laser; and delivering a pulsed laser beam having a second wavelength to the sample point using a tunable pulsed transition laser. The pulsed laser beam having the first wavelength and the pulsed laser beam having the second wavelength have energy sufficient to excite an electron of a sample molecule to a Rydberg state. A level of ionization or light absorption can be detected at the sample point. The level of ionization or light absorption detected and the first and second wavelengths are used to determine the presence and identity of one or more chemicals in the sample.
The present disclosure may be more readily understood by reference to the following drawings wherein:
Even though spectroscopic methods are widely used to analyze substances, their applications are often limited by low sensitivity and an inability to simultaneously identify the ingredients of multi-component mixtures (e.g., gaseous mixtures). Multi-dimensional Rydberg fingerprint spectroscopy can be used for such detection and identification of components of multi-dimensional mixtures (e.g., gaseous mixtures) based on the highly structured and specific absorption spectra of molecules (e.g., when exposed to bursts of light in the vacuum ultraviolet).
Multi-dimensional Rydberg fingerprint spectroscopy can be used for chemical sensing in a sample of a multi-dimensional mixture (e.g., a gaseous mixture). A pulsed laser beam having a first wavelength can be delivered to a sample using a tunable pulsed excitation laser; and a pulsed laser beam having a second wavelength can be delivered to the sample point using a tunable pulsed transition laser. The pulsed laser beam having the first wavelength and the pulsed laser beam having the second wavelength have energy sufficient to excite an electron of a sample molecule to a Rydberg state. A level of ionization or light absorption can be detected at the sample point. The level of ionization or light absorption detected and the first and second wavelengths are used to determine the presence and identity of one or more chemicals in the sample. Taking advantage of the highly molecule-specific energies of molecular Rydberg states, the method uses multiple transition to, and between, Rydberg states to identify the one or more chemicals in the sample.
Excitation to the Rydberg states can be accomplished with 1-photon, 2-photon or higher photon processes. Transitions between Rydberg states can be similarly achieved. The systems and methods described herein advance the state of the art in several ways. First, excitation to the Rydberg states is achieved by 1-photon, 2-photon or higher photon processes. Second, additional transitions between Rydberg states provides additional dimensions of detection. Third, accelerating the charges towards electrodes for detection, where current or voltage measurement is a convenient method to measure ionization signals. And finally, identification of compounds (e.g., H2S) is achieved by characterizing surface contours in highly dimensional space (e.g., greater than 2 dimensions).
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of conflict, the present specification, including definitions, will control.
The terminology as set forth herein is for description of the embodiments only and should not be construed as limiting of the invention as a whole. Unless otherwise specified, “a,” “an,” “the,” and “at least one” are used interchangeably. Furthermore, as used in the description of the invention and the appended claims, the singular forms “a”, “an”, and “the” are inclusive of their plural forms, unless contraindicated by the context surrounding such.
Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).
As used herein, the term “about,” when referring to a value or to an amount of mass, weight, time, volume, concentration or percentage is meant to encompass variations of in some embodiments ±20%, in some embodiments ±10%, in some embodiments ±5%, in some embodiments ±1%, in some embodiments ±0.5%, and in some embodiments ±0.1% from the specified amount, as such variations are appropriate to perform the disclosed method.
The terms “comprising” and variations thereof do not have a limiting meaning where these terms appear in the description and claims.
The conjunctive phrase “and/or” indicates that either or both of the items referred to can be present.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although any methods and materials similar or equivalent to those described herein can be used in the practice for testing of the present invention, the preferred materials and methods are described herein. In describing and claiming the present invention, the following terminology will be used.
Referring now to
The system 10 uses multidimensional Rydberg Fingerprint Spectroscopy, which takes advantage of the concept of multiple transitions between energy levels that are highly specific identifiers of molecular states, to perform chemical sensing to detect and identify components of a sample. Notably, any type of Rydberg Fingerprint Spectroscopy detects electronic transitions in molecules. Electronic transitions in molecules are characterized by absorption cross-sections that are very large compared to vibrational transitions. Additionally, the electronic transitions are attractive for chemical sensing applications because the electronic transitions occur in UV/VIS/NIR wavelength ranges for which high power lasers and highly sensitive detectors are readily available (e.g., excitation laser 12, transition laser 16, detector 20, etc.). Rydberg Fingerprint Spectroscopy is well-suited for chemical identification, exploiting the fact that the spectra of Rydberg binding energies provide a detailed fingerprint of molecular structure that is used for the chemical identification. Rydberg Fingerprint Spectroscopy uses short (e.g., femtosecond) laser pulses to optically excite a valence electron from a neutral molecule into a Rydberg state, an excited electronic state that can be represented by a wave function resembling that of a hydrogen atom because the ionic core interaction with an excited electron can take on the general aspects of the interaction between the proton and electron in the hydrogen atom. It should be noted that the electron orbital of the Rydberg state (also referred to as the Rydberg electron orbital) need not encompass the entire molecule or cluster of molecules, as the shape of that portion that is encompassed by the Rydberg electron orbital may still be characterized in accordance with an aspect of this invention. Alternatively, the molecule or cluster of molecules may be smaller than the Rydberg electron orbital such that it is completely encompassed by the Rydberg electron orbital.
Unlike transitions between valance states, Rydberg-Rydberg and Rydberg-ion transitions reveal highly resolved and purely electronic spectra. Since Rydberg electrons do not contribute substantially to the molecular bonding, the potential energy surfaces and subsequently vibrational wavefunctions in different Rydberg states are almost identical. Vibrational wavefunctions in different Rydberg states are thus orthogonal to each other so that the Frank-Condon envelope for Rydberg-Rydberg or Rydberg-ion transitions are confined to a very narrow band. Therefore, the complexity of Rydberg spectra does not scale with the molecular size, making the technique well suited for detection of polyatomic organic molecules. Another advantage of Rydberg spectroscopy is that the number of Rydberg states in molecules mimics those of atoms.
It should further be noted that the Rydberg Fingerprint Spectroscopy approach contrasts significantly with other types of spectroscopy. IR spectroscopy, for example, provides a sensitive measure of very local regions of a molecule. The frequency of a C═O stretch vibration is determined by the force constant of the carbon-oxygen bond, which is only slightly affected by the immediate surroundings of the carbonyl group. In contrast, the Rydberg states are delocalized over very large volumes, and the energies of these states are therefore sensitive to global aspects of the molecular structure. The data derived from the measured energies of the Rydberg states may then be considered to provide a “fingerprint” of the global, large scale shape of the molecule on interest or, more succinctly, to provide a “Rydberg fingerprint”. Rydberg Fingerprint Spectroscopy allows for differentiation between different isomeric and even conformeric forms of molecules.
To detect the spatial distribution of target chemicals in a multi-component mixture, the system 10 uses a multi-photon resonant spectroscopy, multidimensional Rydberg Fingerprint Spectroscopy. Multidimensional Rydberg Fingerprint Spectroscopy rests on the concept of multiple transitions between energy levels that are highly specific identifiers of molecular states. To reach those states, which are at energies starting at about 6 eV above the molecular ground state, a two-photon excitation is used most generally, although for some compounds a one-photon excitation suffices.
Accordingly, the system 10 employs at least two lasers (excitation laser 12 and transition laser 16, but there may be additional transition lasers) that produce light with at least two different excitation wavelengths (having energy sufficient to excite an electrode of a sample molecule to a Rydberg state) and are aligned/oriented to provide the lights to a point 24 within the sample (or “sample point”). The sample point can be at any range as limited by the depletion of the laser beam due to absorption. In some embodiments, the sample point is at a range from 10 meters to 100 meters from each of the lasers (lasers do not need to be the same distance from the sample, but can be the same distance from the sample). The light produced by each of the lasers can be pulsed light to provide the photons. Moreover, the at least two lasers can be tunable. In some instances, additional parameters can be varied, including one or more Rydberg-Rydberg transition wavelength(s), pulse intensities, time delay, pulse durations of photons, pulse shape, polarization, etc. At least one of the at least two lasers can be a femtosecond laser, which may be tunable and can provide pulsed light, as an example. However, a wide variety of pulsed lasers exist that deliver pulse energies and pulse durations suited for this task.
The number of lasers can each provide a dimension to the system 10. Accordingly, there is a minimum of two dimensions. A higher number of dimensions allows for more specific identification of components. Various applications may choose a higher or lower number of dimensions (with the minimum being two). For example, the system 10 can involve excitation to the sharp spectral features (e.g., with excitation laser 12 producing light with a wavelength in the vacuum ultraviolet region, between 150 nm and 200 nm) and transitions between the different spectral lines (e.g., with one or more transition laser 16 producing light with wavelengths in the visible or near IR portions of the spectrum). Scanning the wavelength of the excitation laser 12 provides one dimension. A wavelength scan of the transition laser 16 provides a second dimension. Further dimensions can be obtained by transitioning yet again to other states, with the practical limitation that each dimension requires a tunable wavelength. In this multi-dimensional space, specific but sparse peaks or shapes reveal each molecular component, offering the opportunity to identify many chemical compounds in parallel. Since the sample is at the focus of the laser beams with a volume on the order of 2-10 nl, the analysis method will work on small amounts of sample. An example use of three lasers is shown in
A detector 20 can be positioned away from the at least two lasers to perform multi-level detection, including detection of a level of ionization or light absorption at the sample point. For example, the detector 20 can be positioned proximal to the sample point. The level of ionization or light absorption detected, in addition to the wavelengths (or other information) can be utilized to determine the presence and an identity of one or more chemicals present in a sample (e.g., a multi-component mixture, such as a gaseous mixture). For example, the timing (or time delay) can be varied between the lasers so that the lights are timed to measure the kinetics of a reaction in the sample, which can indicate the presence of one or more chemicals in the sample.
As shown for example in
Additional selectivity is achieved from optical transition between different Rydberg states, as shown in
Components of the system 10 (e.g., at least the detector 20, but other instances may also include the at least two lasers and/or other components) can be employed with a self-contained sensor. An important limitation arises from the total time it takes to acquire a data set: to fully sample the entire multi-dimensional space might exceed the allowable time allocated to data acquisition. For example, the computing device 22 can store and/or execute one or more algorithms to maximize the information output. For example, a self-contained sensor could include a database with the most important features calculated at the highest possible level of theory to directly match the compound present in the analysis by direct comparison with theoretical results. Other dimensions can be included in these calculations to reduce the probability of possible mismatches.
It should be noted that the lasers (e.g., excitation laser 12 and transition laser 16 shown in
An alternative system design is shown in
Another aspect of the present disclosure can include a method 100 (
As an example, the gaseous mixture can be a breath sample, an air sample, or the like. The sample may include one or more chemicals, like hydrogen sulfide. In this example, the sample can be an air sample obtained from the air near an oil well. In other examples, the presence and identity of a plurality of different chemicals in the sample can be determined. At 102, a pulsed laser beam having a first wavelength (e.g., the first wavelength can have a wavelength from 150 to 200 nanometers) can be delivered to a sample point (e.g., point 24) using a tunable (e.g., by computing device 22 and/or controller 14) pulsed excitation laser (e.g., excitation laser 12). At 104, a pulsed laser beam having a second wavelength (different from the first wavelength) can be delivered to the sample point (e.g., point 24) using a tunable (e.g., by computing device 22 and/or controller 18) pulsed transition laser (e.g., transition laser 16). In some instances, the wavelengths can be timed to measure the kinetics of a reaction in the sample. The pulsed laser beam having the first wavelength and the pulsed laser beam having the second wavelength have energy sufficient to excite an electron of a sample molecule to a Rydberg state (shown in
At 106, a level of ionization or light absorption can be detected at the sample point using an ionization or light absorption detector (e.g., detector 20). The ionization or light absorption detector can be located proximal to the sample point. At 108, the level of ionization or light absorption detected, the first wavelength, and the second wavelength are used (e.g., by computer 22) to determine the presence and identity of one or more chemicals present in the sample (as described above).
The complete disclosure of all patents, patent applications, and publications, and electronically available material cited herein are incorporated by reference. The foregoing detailed description and examples have been given for clarity of understanding only. No unnecessary limitations are to be understood therefrom. The invention is not limited to the exact details shown and described, for variations obvious to one skilled in the art will be included within the invention defined by the claims.
This application claims the benefit of U.S. Provisional Application No. 63/093,477 dated 19 Oct. 2020 and entitled “CHEMICAL SENSING USING MULTI-DIMENSIONAL RYDBERG FINGERPRINT SPECTROSCOPY”, which is hereby incorporated by reference in its entirety for all purposes.
Filing Document | Filing Date | Country | Kind |
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PCT/US2021/055512 | 10/19/2021 | WO |
Number | Date | Country | |
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63093477 | Oct 2020 | US |