The Experts below are selected from a list of 126564 Experts worldwide ranked by ideXlab platform
Ya Cheng - One of the best experts on this subject based on the ideXlab platform.
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generation of raman lasers from nitrogen Molecular Ions driven by ultraintense laser fields
New Journal of Physics, 2018Co-Authors: Jinping Yao, Wei Chu, Zhaoxiang Liu, Jinming Chen, Ya ChengAbstract:Atmospheric lasing has aroused much interest in the past few years. The 'air–laser' opens promising potential for remote chemical sensing of trace gases with high sensitivity and specificity. At present, several approaches have been successfully implemented for generating highly coherent laser beams in atmospheric condition, including both amplified-spontaneous emission, and narrow-bandwidth stimulated emission in the forward direction in the presence of self-generated or externally injected seed pulses. Here, we report on generation of multiple-wavelength Raman lasers from nitrogen Molecular Ions (), driven by intense mid-infrared laser fields. Intuitively, the approach appears problematic for the small nonlinear susceptibility of Ions, whereas the efficiency of Raman laser can be significantly promoted in near-resonant condition. More surprisingly, a Raman laser consisting of a supercontinuum spanning from ~310 to ~392 nm has been observed resulting from a series near-resonant nonlinear processes including four-wave mixing, stimulated Raman scattering and cross phase modulation. To date, extreme nonlinear optics in Molecular Ions remains largely unexplored, which provides an alternative means for air–laser-based remote sensing applicatIons.
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rotational coherence encoded in an air laser spectrum of nitrogen Molecular Ions in an intense laser field
Physical Review X, 2013Co-Authors: Haisu Zhang, Jinping Yao, Wei Chu, Chenrui Jing, Bin Zeng, Hongqiang Xie, S L Chin, Kaoru Yamanouchi, Ya ChengAbstract:When exposed to intense infrared laser pulses of femtosecond duration, molecules such as N${}_{2}$, CO${}_{2}$, and H${}_{2}$O not only become ionized but can also produce lasers as a result of simultaneous population inversion. Scientists look deep into this ``air lasing'' phenomenon in N${}_{2}$ gas and uncover both quantum coherence in the rotational wave packets of the lasing Molecular Ions and its footprint in the air-laser spectrum.
Stefan Willitsch - One of the best experts on this subject based on the ideXlab platform.
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observation of electric dipole forbidden infrared transitIons in cold Molecular Ions
Nature Physics, 2014Co-Authors: Matthias Germann, Xin Tong, Stefan WillitschAbstract:Spectroscopic transitIons in atoms and molecules that are not allowed within the electric-dipole approximation, but occur because of higher-order terms in the interaction between matter and radiation, are termed dipole-forbidden(1). These transitIons are extremely weak and therefore exhibit very small natural linewidths. Dipole-forbidden optical transitIons in atoms form the basis of next-generation atomic clocks(2,3) and of high-fidelity qubits used in quantum information processors and quantum simulators(4). In molecules, however, such transitIons are much less characterized, reflecting the considerable challenges to address them. Here, we report direct observation of dipole-forbidden, electric-quadrupole-allowed infrared (IR) transitIons in a Molecular ion. Their detection was enabled by the very long interrogation times of several minutes afforded by the sympathetic cooling of individual quantum-state-selected Molecular Ions into the nearly perturbation-free environment of a Coulomb crystal. The present work paves the way for new mid-IR frequency standards and precision spectroscopic measurements on single molecules in the IR domain(5).
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millikelvin reactive collisIons between sympathetically cooled Molecular Ions and laser cooled atoms in an ion atom hybrid trap
Physical Review Letters, 2012Co-Authors: Felix H J Hall, Stefan WillitschAbstract:We report on a study of cold reactive collisIons between sympathetically cooled Molecular Ions and laser-cooled atoms in an ion-atom hybrid trap. Chemical reactIons were studied at average collision energies $⟨{E}_{\mathrm{coll}}⟩/{k}_{\mathrm{B}}\ensuremath{\gtrsim}20\text{ }\text{ }\mathrm{mK}$, about 2 orders of magnitude lower than has been achieved in previous experiments with Molecular Ions. Choosing ${\mathrm{N}}_{2}^{+}+\mathrm{Rb}$ as a prototypical system, we find that the reaction rate is independent of the collision energy within the range studied, but strongly dependent on the internal state of Rb. Highly efficient charge exchange four times faster than the Langevin rate was observed with Rb in the excited ($5p$) $^{2}P_{3/2}$ state. This observation is rationalized by a capture process dominated by the charge-quadrupole interaction and a near resonance between the entrance and exit channels of the system. Our results provide a test of classical models for reactIons of Molecular Ions at the lowest energies reached thus far.
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collisional and radiative effects in the state selective preparation of translationally cold Molecular Ions in ion traps
Physical Review A, 2011Co-Authors: Xin Tong, Dieter Wild, Stefan WillitschAbstract:We give a detailed characterization of a recently developed method to prepare translationally cold, internally state-selected Molecular Ions in ion traps [X. Tong, A. H. Winney, and S. Willitsch, Phys. Rev. Lett. 105, 143001 (2010)]. The technique relies on the generation of Molecular Ions in a well-defined rotational-vibrational quantum state using threshold photoionization followed by sympathetic cooling of the translational motion with laser-cooled Ca${}^{+}$ Ions. We discuss the experimental requirements for the successful generation and sympathetic cooling of state-selected Ions, explore the influence of collisional and radiative processes on the population redistribution dynamics, and give an assessment of the scopeof the method.
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sympathetic cooling of Molecular Ions in selected rotational and vibrational states produced by threshold photoionization
Physical Review Letters, 2010Co-Authors: Xin Tong, Alexander H Winney, Stefan WillitschAbstract:We present a new method for the generation of rotationally and vibrationally state-selected, translationally cold Molecular Ions in ion traps. Our technique is based on the state-selective threshold photoionization of neutral molecules followed by sympathetic cooling of the resulting Ions with laser-cooled calcium Ions. Using N-2(+) Ions as a test system, we achieve <90% selectivity in the preparation of the ground rovibrational level and state lifetimes on the order of 15 minutes limited by collisIons with background-gas molecules. The technique can be employed to produce a wide range of apolar and polar Molecular Ions in the ground and excited rovibrational states. Our approach opens up new perspectives for cold quantum-controlled ion-molecule-collision studies, frequency-metrology experiments with state-selected Molecular Ions and Molecular-ion qubits.
S Schiller - One of the best experts on this subject based on the ideXlab platform.
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rotational spectroscopy of cold and trapped Molecular Ions in the lamb dicke regime
Nature Physics, 2018Co-Authors: S Alighanbari, M Hansen, V I Korobov, S SchillerAbstract:Sympathetic cooling of trapped Ions has been established as a powerful technique for the manipulation of non-laser-coolable Ions1–4. For Molecular Ions, it promises vastly enhanced spectroscopic resolution and accuracy. However, this potential remains untapped so far, with the best resolution achieved being not better than 5 × 10−8 fractionally, due to residual Doppler broadening being present in ion clusters even at the lowest achievable translational temperatures5. Here we introduce a general and accessible approach that enables Doppler-free rotational spectroscopy. It makes use of the strong radial spatial confinement of Molecular Ions when trapped and crystallized in a linear quadrupole trap, providing the Lamb–Dicke regime for rotational transitIons. We achieve a linewidth of 1 × 10−9 fractionally and 1.3 kHz absolute, an improvement of ≃50-fold over the previous highest resolution in rotational spectroscopy. As an application, we demonstrate the most precise test of ab initio Molecular theory and the most accurate (1.3 × 10−9) determination of the proton mass using Molecular spectroscopy. The results represent the long overdue extension of Doppler-free microwave spectroscopy of laser-cooled atomic ion clusters6 to higher spectroscopy frequencies and to molecules. This approach enables a wide range of high-accuracy measurements on molecules, both on rotational and, as we project, vibrational transitIons. Doppler-free, ultrahigh-resolution rotational spectroscopy is reported for small Molecular Ions in a linear quadrupole trap. With 10–9 fractional linewidth, this method has a 50-fold improvement over previous reports.
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rotational spectroscopy of cold and trapped Molecular Ions in the lamb dicke regime
Nature Physics, 2018Co-Authors: S Alighanbari, V I Korobov, M. G. Hansen, S SchillerAbstract:Sympathetic cooling of trapped Ions has been established as a powerful technique for the manipulation of non-laser-coolable Ions1–4. For Molecular Ions, it promises vastly enhanced spectroscopic resolution and accuracy. However, this potential remains untapped so far, with the best resolution achieved being not better than 5 × 10−8 fractionally, due to residual Doppler broadening being present in ion clusters even at the lowest achievable translational temperatures 5 . Here we introduce a general and accessible approach that enables Doppler-free rotational spectroscopy. It makes use of the strong radial spatial confinement of Molecular Ions when trapped and crystallized in a linear quadrupole trap, providing the Lamb–Dicke regime for rotational transitIons. We achieve a linewidth of 1 × 10−9 fractionally and 1.3 kHz absolute, an improvement of ≃50-fold over the previous highest resolution in rotational spectroscopy. As an application, we demonstrate the most precise test of ab initio Molecular theory and the most accurate (1.3 × 10−9) determination of the proton mass using Molecular spectroscopy. The results represent the long overdue extension of Doppler-free microwave spectroscopy of laser-cooled atomic ion clusters 6 to higher spectroscopy frequencies and to molecules. This approach enables a wide range of high-accuracy measurements on molecules, both on rotational and, as we project, vibrational transitIons.
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rotational spectroscopy of cold trapped Molecular Ions in the lamb dicke regime
arXiv: Quantum Physics, 2018Co-Authors: S Alighanbari, M Hansen, V I Korobov, S SchillerAbstract:Sympathetic cooling of trapped Ions has been established as a powerful technique for manipulation of non-laser-coolable Ions (Raizen1992,Waki1992,Bowe1999,Barrett2003). For Molecular Ions, it promises vastly enhanced spectroscopic resolution and accuracy. However, this potential remains untapped so far, with the best resolution achieved being not better than $5\times10^{-8}$ fractionally, due to residual Doppler broadening being present in ion clusters even at the lowest achievable translational temperatures (Bressel2012). Here we introduce a general and accessible approach that enables Doppler-free rotational spectroscopy. It makes use of the strong radial spatial confinement of Molecular Ions when trapped and crystallized in a linear quadrupole trap, providing the Lamb-Dicke regime for rotational transitIons. We achieve a line width of $1\times10^{-9}$ fractionally and $1.3~\textrm{kHz}$ absolute, an improvement by $50$ and nearly $3\times10^{3}$, respectively, over other methods. The systematic uncertainty is $2.5\times10^{-10}$. As an application, we demonstrate the most precise test of $\textit{ab initio}$ Molecular theory and the most precise ($1.3~\textrm{PPB}$) spectroscopic determination of the proton mass. The results represent the long overdue extension of Doppler-free microwave spectroscopy of laser-cooled atomic ion clusters (Berkeland1998) to higher spectroscopy frequencies and to molecules. This approach enables a vast range of high-precision measurements on molecules, both on rotational and, as we project, vibrational transitIons.
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blackbody thermometry with cold Molecular Ions and application to ion based frequency standards
Physical Review A, 2007Co-Authors: J C J Koelemeij, Bernhard Roth, S SchillerAbstract:We have used laser spectroscopy to measure the rotational level distribution of trapped Molecular $\mathrm{H}{\mathrm{D}}^{+}$ Ions at translational temperatures in the millikelvin range. The $\mathrm{H}{\mathrm{D}}^{+}$ Ions are loaded into an ion trap by electron-impact ionization, and sympathetically cooled using laser-cooled ${\mathrm{Be}}^{+}$ Ions which are already stored in the trap. Under our experimental conditIons, the internal (rotational) degrees of freedom turn out to be independent of the translational degrees of freedom, and an effective rotational temperature close to room temperature is found. The near absence of background-gas collisIons allows the rotational temperature to be related directly to the temperature of the ambient blackbody radiation (BBR). This feature suggests the use of Molecular Ions for BBR thermometry, which may help to improve the accuracy of frequency standards based on trapped atomic Ions. For the spectroscopic measurement of the rotational populatIons, we propose a nondestructive technique.
V I Korobov - One of the best experts on this subject based on the ideXlab platform.
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rotational spectroscopy of cold and trapped Molecular Ions in the lamb dicke regime
Nature Physics, 2018Co-Authors: S Alighanbari, M Hansen, V I Korobov, S SchillerAbstract:Sympathetic cooling of trapped Ions has been established as a powerful technique for the manipulation of non-laser-coolable Ions1–4. For Molecular Ions, it promises vastly enhanced spectroscopic resolution and accuracy. However, this potential remains untapped so far, with the best resolution achieved being not better than 5 × 10−8 fractionally, due to residual Doppler broadening being present in ion clusters even at the lowest achievable translational temperatures5. Here we introduce a general and accessible approach that enables Doppler-free rotational spectroscopy. It makes use of the strong radial spatial confinement of Molecular Ions when trapped and crystallized in a linear quadrupole trap, providing the Lamb–Dicke regime for rotational transitIons. We achieve a linewidth of 1 × 10−9 fractionally and 1.3 kHz absolute, an improvement of ≃50-fold over the previous highest resolution in rotational spectroscopy. As an application, we demonstrate the most precise test of ab initio Molecular theory and the most accurate (1.3 × 10−9) determination of the proton mass using Molecular spectroscopy. The results represent the long overdue extension of Doppler-free microwave spectroscopy of laser-cooled atomic ion clusters6 to higher spectroscopy frequencies and to molecules. This approach enables a wide range of high-accuracy measurements on molecules, both on rotational and, as we project, vibrational transitIons. Doppler-free, ultrahigh-resolution rotational spectroscopy is reported for small Molecular Ions in a linear quadrupole trap. With 10–9 fractional linewidth, this method has a 50-fold improvement over previous reports.
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rotational spectroscopy of cold and trapped Molecular Ions in the lamb dicke regime
Nature Physics, 2018Co-Authors: S Alighanbari, V I Korobov, M. G. Hansen, S SchillerAbstract:Sympathetic cooling of trapped Ions has been established as a powerful technique for the manipulation of non-laser-coolable Ions1–4. For Molecular Ions, it promises vastly enhanced spectroscopic resolution and accuracy. However, this potential remains untapped so far, with the best resolution achieved being not better than 5 × 10−8 fractionally, due to residual Doppler broadening being present in ion clusters even at the lowest achievable translational temperatures 5 . Here we introduce a general and accessible approach that enables Doppler-free rotational spectroscopy. It makes use of the strong radial spatial confinement of Molecular Ions when trapped and crystallized in a linear quadrupole trap, providing the Lamb–Dicke regime for rotational transitIons. We achieve a linewidth of 1 × 10−9 fractionally and 1.3 kHz absolute, an improvement of ≃50-fold over the previous highest resolution in rotational spectroscopy. As an application, we demonstrate the most precise test of ab initio Molecular theory and the most accurate (1.3 × 10−9) determination of the proton mass using Molecular spectroscopy. The results represent the long overdue extension of Doppler-free microwave spectroscopy of laser-cooled atomic ion clusters 6 to higher spectroscopy frequencies and to molecules. This approach enables a wide range of high-accuracy measurements on molecules, both on rotational and, as we project, vibrational transitIons.
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rotational spectroscopy of cold trapped Molecular Ions in the lamb dicke regime
arXiv: Quantum Physics, 2018Co-Authors: S Alighanbari, M Hansen, V I Korobov, S SchillerAbstract:Sympathetic cooling of trapped Ions has been established as a powerful technique for manipulation of non-laser-coolable Ions (Raizen1992,Waki1992,Bowe1999,Barrett2003). For Molecular Ions, it promises vastly enhanced spectroscopic resolution and accuracy. However, this potential remains untapped so far, with the best resolution achieved being not better than $5\times10^{-8}$ fractionally, due to residual Doppler broadening being present in ion clusters even at the lowest achievable translational temperatures (Bressel2012). Here we introduce a general and accessible approach that enables Doppler-free rotational spectroscopy. It makes use of the strong radial spatial confinement of Molecular Ions when trapped and crystallized in a linear quadrupole trap, providing the Lamb-Dicke regime for rotational transitIons. We achieve a line width of $1\times10^{-9}$ fractionally and $1.3~\textrm{kHz}$ absolute, an improvement by $50$ and nearly $3\times10^{3}$, respectively, over other methods. The systematic uncertainty is $2.5\times10^{-10}$. As an application, we demonstrate the most precise test of $\textit{ab initio}$ Molecular theory and the most precise ($1.3~\textrm{PPB}$) spectroscopic determination of the proton mass. The results represent the long overdue extension of Doppler-free microwave spectroscopy of laser-cooled atomic ion clusters (Berkeland1998) to higher spectroscopy frequencies and to molecules. This approach enables a vast range of high-precision measurements on molecules, both on rotational and, as we project, vibrational transitIons.
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fundamental transitIons and ionization energies of the hydrogen Molecular Ions with few ppt uncertainty
Physical Review Letters, 2017Co-Authors: V I Korobov, Laurent Hilico, Ph J KarrAbstract:We calculate ionization energies and fundamental vibrational transitIons for H_{2}^{+}, D_{2}^{+}, and HD^{+} Molecular Ions. The nonrelativistic quantum electrodynamics expansion for the energy in terms of the fine structure constant α is used. Previous calculatIons of orders mα^{6} and mα^{7} are improved by including second-order contributIons due to the vibrational motion of nuclei. Furthermore, we evaluate the largest correctIons at the order mα^{8}. That allows us to reduce the fractional uncertainty to the level of 7.6×10^{-12} for fundamental transitIons and to 4.5×10^{-12} for the ionization energies.
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hydrogen Molecular Ions for improved determination of fundamental constants
Physical Review A, 2016Co-Authors: Ph J Karr, Laurent Hilico, J C J Koelemeij, V I KorobovAbstract:An experimental scheme is proposed to help resolve the proton- (deuteron-) radius puzzle with rovibrational two-photon spectroscopy of hydrogen Molecular Ions measured at high precision. The technique is also expected to measure other fundamental constants, such as the Rydberg constant and the electron-proton mass ratio, at a competitive level of precision compared to the existing schemes.
Xin Tong - One of the best experts on this subject based on the ideXlab platform.
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observation of electric dipole forbidden infrared transitIons in cold Molecular Ions
Nature Physics, 2014Co-Authors: Matthias Germann, Xin Tong, Stefan WillitschAbstract:Spectroscopic transitIons in atoms and molecules that are not allowed within the electric-dipole approximation, but occur because of higher-order terms in the interaction between matter and radiation, are termed dipole-forbidden(1). These transitIons are extremely weak and therefore exhibit very small natural linewidths. Dipole-forbidden optical transitIons in atoms form the basis of next-generation atomic clocks(2,3) and of high-fidelity qubits used in quantum information processors and quantum simulators(4). In molecules, however, such transitIons are much less characterized, reflecting the considerable challenges to address them. Here, we report direct observation of dipole-forbidden, electric-quadrupole-allowed infrared (IR) transitIons in a Molecular ion. Their detection was enabled by the very long interrogation times of several minutes afforded by the sympathetic cooling of individual quantum-state-selected Molecular Ions into the nearly perturbation-free environment of a Coulomb crystal. The present work paves the way for new mid-IR frequency standards and precision spectroscopic measurements on single molecules in the IR domain(5).
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collisional and radiative effects in the state selective preparation of translationally cold Molecular Ions in ion traps
Physical Review A, 2011Co-Authors: Xin Tong, Dieter Wild, Stefan WillitschAbstract:We give a detailed characterization of a recently developed method to prepare translationally cold, internally state-selected Molecular Ions in ion traps [X. Tong, A. H. Winney, and S. Willitsch, Phys. Rev. Lett. 105, 143001 (2010)]. The technique relies on the generation of Molecular Ions in a well-defined rotational-vibrational quantum state using threshold photoionization followed by sympathetic cooling of the translational motion with laser-cooled Ca${}^{+}$ Ions. We discuss the experimental requirements for the successful generation and sympathetic cooling of state-selected Ions, explore the influence of collisional and radiative processes on the population redistribution dynamics, and give an assessment of the scopeof the method.
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sympathetic cooling of Molecular Ions in selected rotational and vibrational states produced by threshold photoionization
Physical Review Letters, 2010Co-Authors: Xin Tong, Alexander H Winney, Stefan WillitschAbstract:We present a new method for the generation of rotationally and vibrationally state-selected, translationally cold Molecular Ions in ion traps. Our technique is based on the state-selective threshold photoionization of neutral molecules followed by sympathetic cooling of the resulting Ions with laser-cooled calcium Ions. Using N-2(+) Ions as a test system, we achieve <90% selectivity in the preparation of the ground rovibrational level and state lifetimes on the order of 15 minutes limited by collisIons with background-gas molecules. The technique can be employed to produce a wide range of apolar and polar Molecular Ions in the ground and excited rovibrational states. Our approach opens up new perspectives for cold quantum-controlled ion-molecule-collision studies, frequency-metrology experiments with state-selected Molecular Ions and Molecular-ion qubits.
