Laser-microwave Double Resonance Research Articles

Hyperfine structure constant of the neutron halo nucleus (11)Be(+).

The hyperfine splittings of ground state Be+11 have been measured precisely by laser-microwave double resonance spectroscopy for trapped and laser cooled beryllium ions. The ions were produced at relativistic energies and subsequently slowed down and trapped at mK temperatures. The magnetic hyperfine structure constant of Be+11 was determined to be A11=-2677.302 988(72) MHz from the measurements of the mF-mF'=0-0 field independent transition. This measurement provides essential data for the study of the distribution of the halo neutron in the single neutron halo nucleus Be11 through the Bohr-Weisskopf effect.

Study of laser-pumped double-resonance clock signals using a microfabricated cell

We present our microwave spectroscopic studies on laser–microwave double-resonance (DR) signals obtained from a micro-fabricated Rb vapor cell. This study focuses on the characteristics and systematic shifts of the ground-state ‘clock transition’ in 87Rb (| Fg = 1,mF = 0⟩ → |Fg = 2, mF = 0⟩) used in Rb atomic clocks, and represents a first step toward a miniature atomic clock based on the DR scheme. A short-term clock instability below 2 × 1011τ−1/2 is demonstrated, staying below 10−11 up to τ = 104 s.

Developments at the SLOWRI facility at RIKEN: precision optical spectroscopy of 7,9,10,11Be+ ions

Precision optical spectroscopy of radioactive Be isotopes produced in projectile fragmentation has been performed for the first time at the prototype SLOWRI facility of RIKEN RI-Beam Factory. The ground state hyperfine constants of 7Be+ and 11Be+ were determined with relative accuracies of 6 × 10−7 and 3 × 10−8, respectively, by laser-microwave double resonance spectroscopy of laser-cooled ions in a trap. The optical transition energies from the ground S-state to the excited P-state of Be isotope ions were also measured to determine the nuclear charge radii from the isotope shifts. Development of the universal slow RI-beam facility—SLOWRI—based on the rf-carpet ion guide technique is progressing at RIKEN RI-beam factory. An additional capability of providing parasitic slow RI-beams from the projectile fragment separator BigRIPS is also discussed.

Structural studies of biomolecules in the gas phase by chirped-pulse Fourier transform microwave spectroscopy

Studies of the gas phase structures of biomolecules provide an important connection to theoretical methods for modeling large molecular structures. The key features of biomolecule structures, such as their conformational flexibility and the complexes they form through intermolecular interactions, pose major challenges to spectroscopic techniques. Rotationally resolved spectroscopy holds the possibility of true structure determination where analysis of the spectra of isotopic species provides actual atom positions in the three-dimensional structure. Molecular rotational spectroscopy is ideally suited for this type of study because it offers high spectral resolution and is generally applicable (requiring only a polar molecule). A chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer has been optimized for biomolecular spectroscopy. The sensitivity of this technique makes it possible to perform heavy atom (13C, 15N, 18O) structure determination using the natural abundance of the isotopes. The performance of the spectrometer is illustrated by obtaining the structure of the phenol dimer, a model system that is a challenge for theoretical methods. For application to larger biomolecule systems, it is expected that rotational spectroscopy alone will face challenges in making structural determinations. The scope of problems that can be addressed by rotational spectroscopy can be expanded through double-resonance spectroscopy approaches that provide a "second dimension" of structural information. A general method to implement laser-microwave double resonance spectroscopy is described. We also discuss the potential for developing low-cost microwave detectors for biomolecular spectroscopy that achieve savings by reducing the measurement bandwidth. This approach is particularly promising for developing low-frequency CP-FTMW spectrometers that are well-suited for large molecule rotational spectroscopy.

Ion trap nuclear resonance on $\mathsf{^{151}Eu^ + }$

Laser-microwave double resonance techniques applied to a cloud of a natural mixture of Eu + isotopes confined in a Penning trap has been used to induce and detect nuclear Zeeman transitions. In spite of the complex level structure of Eu + and overlapping spectra from the two isotopes five different $\Delta m_I = 1$ transitions could be observed from which the nuclear magnetic moment can be derived. We obtain for 151 Eu + g I = 1.377 34(6) demonstrating the potential for high accuracy of the technique. The experiment can be considered as a feasibility test that precise spectroscopy data using the ion storage technique can be obtained of very complex ions and under unfavourable conditions.

Laser-microwave spectroscopy of the hyperfine structure of 9Be for the investigation of unstable Be isotopes

For an investigation concerning the nuclear magnetic moments and their distributions in the nuclei of 7,11Be, an experimental project using laser-microwave double resonance spectroscopy for trapped ions is under progress at INS. Laser cooled ion crystals consisting of a few 9Be + ions were observed and the ground state hyperfine splitting of 9Be + was measured with a precision of 10 −5. Experiments on the unstable isotope 7Be have been started.

IR–microwave double resonance studies of dipole moments in the ν1 and ν3 states of ammonia

Infrared laser–microwave double resonance spectroscopy is used to observe the Stark effect of tunneling transitions within the ν1 and ν3 hydrogen stretching states of NH3. Dipole moments for 11 J,K states of ν1 and 3 J,K states of ν3 are measured to high accuracy. These data, combined with previous measurements in the ground and excited bending states, give a dipole moment function (in Debye) of: μv1v2v3v4=1.5610+7.2×10−3(v1+1/2)−2.271×10−1(v2+1/2)+3.75×10−2(v3+1)−1.65×10−2(v4+1). μe=1.561 D is the first experimental measurement of the NH3 equilibrium moment. These results are also used to analyze and recalculate the dipole moment measured by Shimizu and co-workers in a vNH=5 excited state of NH3.

IR–Microwave Double Resonance Studies of Tunneling Frequencies in the ν1and ν3States of Ammonia

Infrared laser-microwave double resonance spectroscopy has been used to observe tunneling transitions in the ν1and ν3hydrogen stretching states of NH3. Inversion frequencies in 15 rotational states of ν1and 6 rotational states of ν3were measured to accuracies of ±25 kHz. Comparisons between ground state andv1= 1 data indicate thatx–yCoriolis interactions are responsible for much of the angular momentum dependence of the ν1inversion splittings. TheJ,Krotational quantum number dependence for tunneling in ν3is very different from that in either the ground state or ν1.

A laser-microwave double resonance for unstable nuclear ions

We report the results of laser-microwave double resonance spectroscopy of laser cooled 9Be+ ions trapped in a linear rf trap. The microwave transition frequency between the sublevels of the 9Be+ ground state hyperfine structure in a weak magnetic field was measured with a precision of 5 × 10−6. This experiment has been carried out as a first step of our project to study the hyperfine anomaly of unstable nuclear ions at INS.

Color Center Laser–Microwave Double Resonance Spectroscopy of the ν1Vibrational State of HCCF

Rotational transitions of fluoroacetylene in the ν1(CH stretch) vibrational state have been observed by the laser–microwave double resonance technique using a color center laser as a radiation source in the 3 μm region. The rotational constant and centrifugal distortion constant in the ν1state were determined to be 9684.310(16) MHz and 2.68(62) kHz, respectively, where the uncertainties given in parentheses correspond to 2.5 standard deviations.

Experimental gJ factor in the metastable 5D3/2 level of Ba+

The Zeeman splitting of the metastable 5${\mathit{D}}_{3/2}$ level of $^{138}\mathrm{Ba}^{+}$ in a magnetic field of 6 T has been measured in a laser-microwave double resonance experiment in a Penning ion trap. The magnetic field at the ion's position is determined by the cyclotron frequency of electrons stored in the same trap. From the ratio of both transition frequencies we obtain a ${\mathit{g}}_{\mathit{J}}$ value of 0.799 327 8(3). As a by-product, we confirmed earlier measurements on the 6${\mathit{S}}_{1/2}$ ground-state ${\mathit{g}}_{\mathit{J}}$ factor to 2.002 492 2(10). The precision in both experiments is sufficient to test relativistic many-body calculations. \textcopyright{} 1996 The American Physical Society.

High-resolution microwave spectroscopy on trapped ion clouds

Ion traps are particular usefully devices for precision spectroscopy on ionic ground states in the microwave domain. Although ultimate precision is achieved only with laser-cooled single ions, in many cases the precision obtained using large uncooled clouds of ions is sufficient for many requirements in atomic physics. The stronger signal in this case makes possible experiments on forbidden transitions or on systems with complex spectra and many substates. Recent examples of laser-microwave double resonance spectra on Pb+ and Eu+ are presented along with attempts to laser-cool a large ion cloud in order to reduce uncertainties from the second-order Doppler effect.

Precise determination of the ground state hyperfine structure splitting of43Ca II

We have performed a laser microwave double resonance experiment on43Ca+ ions stored in a Paul ion trap. The ground state hfs splitting has been determined to Δν=3 225 608 286. 4(3) Hz. The value is corrected for small Zeeman, Stark and second order Doppler shifts as well as for light shift effects caused by the laserfields. The uncertainty is mainly determined by the errors of these corrections.

A precision measurement of the hyperfine structure of87Sr+

The ground state hyperfine splitting of87Sr+ was measured with a precision of 1×10−8. The experiments were performed with an RF ion trap connected to an ISOL (isotope separator on-line), where all the possible transitions between Zeeman sublevels were observed by a laser-microwave double resonance method. The magnetic dipole hyperfine constant was determined to beA=−1 000 473.673 (11) kHz.

赤外レーザーマイクロ波二重共鳴法による分子の電気的性質の精密測定

赤外レーザーマイクロ波二重共鳴法による分子の電気的性質の精密測定

High-Resolution Vibrational Spectra of Furazan

Abstract The study by Fourier transform (FT) infrared (IR) spectroscopy of the fundamental vibrational bands v12 and v5 of furazan yields the origins of these bands with a statistical uncertainty of 10-6 cm-1, which leads to an estimated absolute uncertainty of 10-4 cm-1. The values are v°12 = 952.6123 cm -1 and v°5 = 1.005.3536 cm -1. They confirm the values previously deduced from laser/microwave double resonance (LMDR) experiments. Previous results for the molecular constants of the vibrational ground state and of the two vibrationally excited states, as obtained by double resonance modulation (DRM) microwave spectroscopy alone, are confirmed and refined. Advantages brought about through the combination of the DRM microwave and the FT-IR technique are outlined.

Vibrational Band Origins of the Fundamentals v12 and v5 of Furazan from Laser/Microwave Double Resonance

Information from rotational spectroscopy has been utilised for the interpretation of experimental results from laser/microwave double resonance (LMDR) experiments on furazan. The band origins v0 for the fundamental vibrations v12 and v5 have been deduced from these experiments as v0 12 = 952.611 (2) cm -1 and = 1005.353(2] cm-1 General implications of the approach and of the LMDR technique are considered.

ChemInform Abstract: CO2 Laser‐Microwave Double Resonance Spectroscopy of HCNO: Precise Measurement of the Dipole Moment and Its Vibrational Dependence.

Abstract The HCNO molecule was investigated by laser-microwave double resonance (LMDR) with a strong electric field. Stark Lamb-dip spectra due to the 2 ν 4 [000(20) 0 ← 000(00) 0 ] and 2 ν 4 + ν 5 − ν 5 [000(21) 1 ← 000(01) 1 ] bands, where ν 4 and ν 5 denote the CNO and HCN bending modes, respectively, were observed with the CO 2 laser lines in the 9.4-μm region. More than 30 LMDR signals associated with these infrared transitions were detected, which were ascribed to rotational transitions in the 000(00) 0 , 000(01) 1 , 000(20) 0 , and 000(21) 1 vibrational states. Dipole moments were determined for these vibrational states with an accuracy better than 10 −4 D. The dipole moments in the ground and ν 5 vibrational states are 3.099345(65) D and 2.910195(58) D, respectively, with the 2.5σ uncertainties in parentheses, the difference being δμ 5 = −0.189150(85) D. The abnormally large dipole moment change caused by the excitation of the HCN bending vibration is discussed in connection with the peculiar potential governing the bending motion. The 2 ν 4 and 2 ν 4 + ν 5 − ν 5 band origins derived from the Stark Lamb-dip spectra are 1069.92955(23) and 1067.63291(8) cm −1 , respectively. Stark Lamb-dip spectra were also observed for the ν 4 + 2 ν 5 [000(12) 1 ← 000(00) 0 ] band, for which two subband origins at 1032.79764(10) and 1077.4378(15) cm −1 were derived, corresponding to the two possible Π ( l = 1) substates of the ν 4 + 2 ν 5 vibrational state. Dipole moments were determined for both substates.

CO 2 laser-microwave double resonance spectroscopy of HCNO: Precise measurement of the dipole moment and its vibrational dependence

The HCNO molecule was investigated by laser-microwave double resonance (LMDR) with a strong electric field. Stark Lamb-dip spectra due to the 2 ν 4[000(20) 0 ← 000(00) 0] and 2 ν 4 + ν 5 − ν 5 [000(21) 1 ← 000(01) 1] bands, where ν 4 and ν 5 denote the CNO and HCN bending modes, respectively, were observed with the CO 2 laser lines in the 9.4-μm region. More than 30 LMDR signals associated with these infrared transitions were detected, which were ascribed to rotational transitions in the 000(00) 0, 000(01) 1, 000(20) 0, and 000(21) 1 vibrational states. Dipole moments were determined for these vibrational states with an accuracy better than 10 −4 D. The dipole moments in the ground and ν 5 vibrational states are 3.099345(65) D and 2.910195(58) D, respectively, with the 2.5σ uncertainties in parentheses, the difference being δμ 5 = −0.189150(85) D. The abnormally large dipole moment change caused by the excitation of the HCN bending vibration is discussed in connection with the peculiar potential governing the bending motion. The 2 ν 4 and 2 ν 4 + ν 5 − ν 5 band origins derived from the Stark Lamb-dip spectra are 1069.92955(23) and 1067.63291(8) cm −1, respectively. Stark Lamb-dip spectra were also observed for the ν 4 + 2 ν 5 [000(12) 1 ← 000(00) 0] band, for which two subband origins at 1032.79764(10) and 1077.4378(15) cm −1 were derived, corresponding to the two possible Π ( l = 1) substates of the ν 4 + 2 ν 5 vibrational state. Dipole moments were determined for both substates.

Molecular-beam spectroscopy of high-temperature species with narrow-band dye lasers

Tunable dye lasers revolutionized molecular spectroscopy. In combination with molecular-beam techniques they helped to create a multitude of new experiments. Optical-optical double resonance, laser-microwave double resonance, and new Stark effect spectroscopy methods are reviewed, which allow investigation of a large class of molecular species including radicals and small clusters.