Zero-field Frequency Research Articles

Laser Stark spectroscopy of 1,1 difluoroethylene at λ = 337 μm

Laser Stark spectra are given for 1,1 difluoroethylene (H 2CCF 2) using laser λ = 337 μm. Three families of resonances are analyzed, two of them being the related transitions J( K a , K c ) = 47(40, 8) ← 46(40, 7) and 47(40, 7) ← 46(40, 6). Relationships between the two transitions permit the calculation of both the zero-field transition frequencies and the effective dipole moment. A third family is assigned as 38(32, 7) ← 37(30, 8). The Stark shift is quasi-linear with E field, dominated by near-degenerate doublet interactions. Extended measurements and a reanalysis of the microwave spectrum are reported, in connection with the analysis of the far infrared spectrum.

Effects of the dipole interaction in superfluidB3

The effects of the dipole interaction on the equilibrium and nonequilibrium properties of /sup 3/He-B are calculated using the quasiclassical theory. In zero field, the dipole interaction distorts the l = 1 gap, generates an l = 3 gap, and induces a new rotated planar phase next to the normal-state transition. The field dependence of the Leggett angle theta/sub L/ is calculated to order (..gamma..H/..delta..)/sup 2/, including the effect of nonquasiparticle corrections. Using the equilibrium properties as input, we calculate the zero-field NMR frequencies in the collisionless regime. A calculation of the field dependence of the longitudinal NMR frequency reveals the existence of a Fermi-liquid oscillation term due to the out-of-phase motion of the normal and superfluid components. Finally, we compare the collisionless and hydrodynamic theories of NMR.

Laser Stark spectroscopy of phosphine

A laser Stark spectrum of PH3 has been observed by using 12C16O2, 13C16O2, 12C18O2, and N2O lasers. Coincidences have been found for 44 ν2 band lines and 31 ν4 band lines for Stark fields up to 60 kV/cm. Zero-field frequencies of the ν2 and ν4 band lines and several A1A2 splittings in the ν2 and ν4 states have been determined. Effective dipole moments for rotational levels in the ν2 and ν4 states have been determined and analyzed by taking into account the mixing of the states resulting from the Coriolis interaction between the ν2 and ν4 states and by introducing the transverse dipole moment between the two states.

Field-Induced Shift in the Longitudinal NMR Frequency of Superfluid 3He–B

The shift in the longitudinal NMR frequency of superfluid 3He-B due to the application of a magnetic field H up to 4.6kG has been measured over a wide range of pressure. We have fit a polynomial in H2 to the data and determined the zero-field frequency, and the coefficients of H2 and H4 as functions of temperature and pressure.

High-precision millimeter-wave spectroscopy with a Stark-sweep method.

A Fabry-Perot interferometer with a hybrid Stark structure has been employed to measure the frequencies of some rotational transitions of ${\mathrm{CH}}_{3}$F and ${\mathrm{CH}}_{3}$OH in the ground vibrational state. The measurements are performed at fixed source frequency by sweeping the Stark field, and the zero-field frequencies are obtained by extrapolation of many different components. The results are \ensuremath{\nu}(K=1)=153 207 755.95(0.83) kHz and \ensuremath{\nu}(K=2)=153 199 847.83(0.40) kHz for the J=3\ensuremath{\leftarrow}2 lines of ${\mathrm{CH}}_{3}$F and \ensuremath{\nu}=76 509 651.3(3.3) kHz for the (5,0)\ensuremath{\leftarrow}(4,1) ${E}_{1}$ transition of ${\mathrm{CH}}_{3}$OH.

Laser Stark spectroscopy of the coriolis coupled ν2 and ν5 bands of CD 3Cl

About 940 Stark resonances for CD 3 35Cl and 610 resonances for CD 3 37Cl have been measured by using a CO 2 laser with the 9- and 10-μm regions. They were assigned to 59 rovibrational transitions of ν 2 ( J′ ≤ 37, K ≤ 14) and 200 of ν 5 ( J′ ≤ 47, −14 ≤ k′ l′ ≤ +10) for 35Cl, and 31 of ν 2 ( J′ ≤ 12, K ≤ 10) and 175 of ν 5 ( J′ ≤ 46, −14 ≤ k′ l′ ≤ +9) for 37Cl. These data, combined with the microwave and FIR data in the ν 2 and ν 5 states, were analyzed by taking account of the Coriolis interaction between ν 2 and ν 5, and the (2, 2) and (2, −1) interactions in ν 5. Several Δ K = +2 transitions of the ν 5 band were observed in the Stark spectra, and the ground state constants, A 0 and D K0 , were determined precisely for both 35Cl and 37Cl species. Also, the vibrationally induced dipole moments were obtained. The molecular constants and the zero-field transition frequencies of the ν 2 and ν 5 bands were determined.

Experimental Results on a Mg Atomic Beam

Recent advances in the realization of a frequency standard based on the fine structure transition 3P1-3P0 of 24Mg are reported. With the frequency stability obtained in the present setup, the zero-field transition frequency is evaluated to be 601 277 158.33 ± 0.2 kHz. The feasibility of a frequency standard with an ultimate uncertainty of 10-13 in a measurement time of less than 10 s is discussed.

K=3 doubling in the v2=1 state of PH3 studied by laser-Stark spectroscopy

Electric field induced transitions A1← A1 and A2←A2 have been observed in the laser-Stark saturation spectrum of qP(5,3), qP(7,3), and qR(8,3) ν2 transitions of PH3. In addition to the zero-field frequency differences Δν=νPH3−νlaser, we obtained the K=3 splittings for J=5 and 7 in the ground state, and for J=4 and 9 in the v2=1 state.

Optoacoustic laser Stark spectroscopy in the ν2 band of 14NH 3

Laser Stark spectroscopy of the R(5, K) transitions in the ν 2 band of ammonia was carried out using coincidences with the 9-μm band CO 2 laser lines. We observed 22 Doppler-free resonances by using an optoacoustic detector and a Lamb-dip stabilized CO 2 laser. A simultaneous analysis of sa, aa, and ss lines yields zero-field transition frequencies with an absolute accuracy of 1 ∼ 2 MHz.

Interaction Effects on the Zeeman Splitting of Collective Modes in SuperfluidHe3-B

Exact calculations of the $B$-phase collective-mode frequencies in a magnetic field are presented, and they provide new information about the effective mass, the pairing interaction, and the Landau parameters. The calculation of the Zeeman splitting for the 2+ mode (real squashing mode) is consistent with the zero-field frequency and agrees quantitatively with the measurements of Avenel et al., for a range of values of ${m}^{*}$ which includes some, but not all, of the differing experimental results for this important parameter.

Laser magnetic resonance measurement of rotational transitions in the metastable a1Δ g state of oxygen

Laser magnetic resonance (LMR) for five rotational transitions, J = 4 ← 3, 5 ← 4, 7 ← 6, 8 ← 7, 9 ← 8, of the oxygen molecule 16O 16O in its metastable state, a 1Δ g , v = 0, are observed using six fir laser lines. Taking the known values of the g factors, their zero-field frequencies are obtained as 340.0085(6), 424.9810(9), 594.870(1), 679.780(1), and 764.658(1) GHz, respectively. They are fit by ( E h ) = B 0[J(J + 1) − 4] + D 0[J(J + 1) − 4] 2 + (−1) J ( 1 2 )qJ (J + 1)[J(J + 1) − 2] , where B 0 = 42.50457(10) GHz, D 0 = 153.14(110) kHz, and q = 0.050(90) kHz.

NMR study of the3dferromagnetic metals: Critical region and paramagnetic phase

The ferromagnetic transition metals iron, nickel, and cobalt have been investigated by nuclear magnetic resonance up to the critical region and, in the case of nickel and cobalt, in the paramagnetic phase. The measurements include the zero-field resonant frequency, spin-spin relaxation rate, and spin-lattice relaxation rate in the ferromagnetic phase, and the Knight shift and spin-lattice relaxation rate in the paramagnetic phase. The data yield values of the static critical exponent ($\ensuremath{\beta}$) for the spontaneous magnetization and the dynamic exponent ($z$) for spin fluctuations near the critical points of all three ferromagnetic metals. Paramagnetic-phase data for nickel and cobalt yield the $d$-spin hyperfine coupling and the orbital Knight shift and susceptibility contributions. Magnetic equation-of-state parameters are derived for nickel and cobalt. Noncritical spin-spin relaxation rates in the ferromagnetic phase are attributed mainly to Suhl-Nakamura interactions, but in bulk metal samples the rates exhibit a striking and unexplained maximum between room temperature and the critical point.

Laser-Stark spectrum of methyl alcohol at 890.761 GHz with the HCN laser

The laser-Stark spectrum of methanol has been studied up to Stark fields of about 55 kV/cm with the 890.761-GHz HCN laser, in both parallel and perpendicular polarizations. Extensive series of absorption lines have been assigned to the J = 6 to 15 members of the k = 6 ← 5 Q branch of the v = 0 E torsional state of CH 3OH. Also, 21 M components of the J k = 7 1 ← 6 2 A ± doublet in the v = 1 excited torsional state have been identified. Efforts to analyze the Q-branch spectra in terms of dipolar parameters and zero-field frequencies were hampered by very high statistical correlations in the least-squares fits. However, it proved necessary to permit the upper-state value of μ a to exceed that of the lower state, by 0.0014 D, and to introduce J dependence of μ a . Analysis of the Stark shifts of the excited torsional state transition yielded a μ a of 0.93 D, about 0.04 D greater than the mean value for the ground state.

Dynamical effects of the interaction between 4f electrons and optical phonons in rare-earth hydroxides, especially in Tb(OH)3and Nd(OH)3

The Raman spectra of single crystals of Nd(OH)3, Gd(OH)3, Tb(OH)3 and of Y(OH)3 have been investigated at helium temperatures and partially in external magnetic fields B<or=12 T. The Raman active optical frequencies have been assigned and the frequencies of the k=0 modes determined and correlated with the modes in the isomorphous rare-earth trichlorides. The interaction between the optical phonons and the 4f electrons becomes apparent in the magnetic phonon splitting in the zero-field frequency shift and, in favourable circumstances, in a phonon-electron anticrossing which depends on the magnetic field. In Tb(OH)3 all these effects can be observed simultaneously. In the same crystal the magnetic phonon splitting occurs spontaneously below its ferromagnetic Curie temperature. All effects can be treated theoretically using a Jahn-Teller type interaction Hamiltonian bilinear in the electron and phonon variables. The numerical values of the coupling constants have been found to agree for the different interaction effects. There are indications of a systematic variation of these numbers with the type of rare-earth ion and the phonon mode considered. The contribution of optical phonons to the effect of interionic energy transfer in Tb(OH)3 by virtual phonon exchange is considered and compared with the aforementioned results.

Nuclear Antiferromagnetic Resonance in SolidHe3

Detailed measurements of the low-field antiferromagnetic resonance spectrum of spin-ordered bcc $^{3}\mathrm{He}$ exhibit large shifts from the Larmor frequency, with a zero-field resonant frequency near zero temperature of $\frac{{\ensuremath{\Omega}}_{0}}{2\ensuremath{\pi}}\ensuremath{\simeq}825$ kHz. Analysis of the spectrum leads to stringent constraints on possible sublattice structures. The temperature dependence of ${\ensuremath{\Omega}}_{0}$ shows low-temperature behavior expected from spin-wave theory, and indicates a first-order transition at 1.03 mK.

Demagnetizing Effects on Antiferromagnetic Resonance in CsNiF3

Antiferromagnetic resonance in CsNiF 3 has been investigated at 35, 24 and 9 GHz bands between T =1.3 K and the Neel temperature ( T N =2.61 K). The resonance frequencies are seriously dependent on sample shape. The results can be understood by a molecular field theory including both the surface demagnetization and the Lorentz fields. The critical field of the phase transition from the spin-flop to the paramagnetic phase has been obtained. The data at T =1.4 K allow a determination of the parameters: antiferromagnetic interchain exchange field H E =990 ±50 Oe, in-plane anisotropy field H A1 =210 ±20 Oe and sublattice magnetization M =96 ±5 emu/cm 3 . The in-plane anisotropy due to the dipolar interaction is estimated to be 245 Oe in reasonable agreement with the observation. From the zero-field gap frequency a large negative anisotropy along the c -axis is dtermined to be H A2 =60 ±3 kOe or D / k =9.2 ±0.5 K.

NMR Study of Magnetic State of Co in Pseudobinary (Y1-xGdx)Co2System

The spin echo NMR of 59 Co in the (Y 1- x Gd x )Co 2 system was observed in both magnetically ordered and paramagnetic states. In YCo 2 , the Knight shift of 59 Co was found to be linear in susceptibility, leading to a hyperfine coupling constant of -89 kOe/ µ B . The zero-field center frequency in the ordered state and both the Knight shift and the relative integrated intensity in the paramagnetic state were observed for over all the concentration. The field dependence of integrated intensity and temperature dependence of Knight shift were also measured in the vicinity of the critical concentration. The results indicate the coexistence of two types of Co atoms in the whole concentration range; one has a magnetic moment which couples antiparallel with the Gd moment and the other has no moment.

A high temperature ODMR study of the two crystalline phases of benzil

We describe a fast ODMR technique, permitting study of phosphorescent triplet states at temperatures not accessible by the usual methods of optical detection. We observe discontinuities in the zero-field transition frequencies of benzil at its phase-transition temperature.

Magnetization and Magnetic Resonance of Antiferromagnetic MnCl22H2O

Magnetization and antiferromagnetic resonance studies were done on a single crystal of MnCl 2 ·2H 2 O at liquid helium temperatures using pulsed magnetic fields up to 180 kOe. The spin-flop phenomenon was observed at 30.2±0.3 kOe under a field along the spin easy b -axis. Transition from antiferromagnetic to paramagnetic states was observed at 154±2, 142±2 and 152±2 kOe when an external field was applied parallel to the a , b and c -axes, respectively. Antiferromagnetic resonance absorptions were observed in the frequency range from 22 to 85 GHz and a zero-field frequency was determined to be 85±1 GHz. The antiferromagnetic exchange field H E and the orthorhombic anisotropy fields H A 1 and H A 2 due to the crystalline field constants D and E were found to be 71.7±1 kOe, 6.0±0.3 kOe, 4.5±0.5 kOe, respectively. It was also found that the second easy axis is the a -axis.

The EPR spectrum of the HO 2 radical and determination of ground state parameters

The detection of lines in the gas phase EPR spectrum of the HO 2 radical at a frequency of 9 GHz is reported. The measurements are combined with the data from the far infrared LMR spectrum and with the zero-field frequencies in the microwave spectrum and fitted to determine a very nearly complete set of ground state parameters. A theoretical relationship is used in order to determine all the non-zero components of the spin rotation tensor ϵ in the principal inertial axis system. The spin-rotation interaction is interpreted in terms of the admixture of both the A ̃ 2A′ state and higher 2 A′ states. The three principal components of the electron spin g-tensor are determined by the magnetic resonance data and are found to be well predicted by Curl's relationship from the spin-rotation tensor. In addition, it was found to be necessary to include terms from the rotational Zeeman effect to obtain a satisfactory fit of the data. Two of the principal components of the rotational g-tensor are determined; the valuefor g r aa is shown to be consistent with Coriolis mixing of the A ̃ 2A′ state. The hyperfine parameters determined in the fit of the microwave data are interpreted in terms of a simple molecular orbital description. The results suggest that about 27% of the spin density is on the central O atom.