Hyperfine Structure Of Transitions Research Articles

Search for Ultralight Dark Matter with Spectroscopy of Radio-Frequency Atomic Transitions.

The effects of scalar and pseudoscalar ultralight bosonic dark matter (UBDM) were searched for by comparing the frequency of a quartz oscillator to that of a hyperfine-structure transition in ^{87}Rb, and an electronic transition in ^{164}Dy. We constrain linear interactions between a scalar UBDM field and standard-model (SM) fields for an underlying UBDM particle mass in the range 1×10^{-17}-8.3×10^{-13} eV and quadratic interactions between a pseudoscalar UBDM field and SM fields in the range 5×10^{-18}-4.1×10^{-13} eV. Within regions of the respective ranges, our constraints on linear interactions significantly improve on results from previous, direct searches for oscillations in atomic parameters, while constraints on quadratic interactions surpass limits imposed by such direct searches as well as by astrophysical observations.

Gravitational Collider Physics via Pulsar–Black Hole Binaries II: Fine and Hyperfine Structures Are Favored

Abstract A rotating black hole can be clouded by light bosons via superradiance and thus acquire an atom-like structure. If such a gravitational atom system is accompanied by a pulsar, the pulsar can trigger transitions between energy levels of the gravitational atom, and these transitions can be detected by pulsar timing. We show that in such pulsar–black hole systems, fine and hyperfine structure transitions are more likely to be probed than the Bohr transition. Also, the calculation of these fine and hyperfine structure transitions are under better analytic control. Thus, these fine and hyperfine structure transitions are more ideal probes in the search for gravitational collider signals in pulsar–black hole systems.

The CH radical at radio wavelengths: revisiting emission in the 3.3 GHz ground-state lines

Context. The intensities of the three widely observed radio-wavelength hyperfine structure (HFS) lines between the Λ-doublet components of the rotational ground state of CH are inconsistent with local thermodynamic equilibrium (LTE) and indicate ubiquitous population inversion. While this can be qualitatively understood assuming a pumping cycle that involves collisional excitation processes, the relative intensities of the lines and in particular the dominance of the lowest frequency satellite line are not well understood. This has limited the use of CH radio emission as a tracer of the molecular interstellar medium. Aims. We aim to investigate the nature of the (generally) weak CH ground-state masers by employing synergies between the ground-state HFS transitions themselves and the far-infrared lines near 149 μm (2 THz) that connect these levels to the first HFS-split, rotationally excited level of the 2Π1∕2 spin–orbital manifold. Methods. We present the first interferometric observations of the CH 9 cm ground-state HFS transitions at 3.264 GHz, 3.335 GHz, and 3.349 GHz towards the four high-mass star-forming regions (SFRs) Sgr B2 (M), G34.26+0.15, W49 (N), and W51 made with the Karl G. Jansky Very Large Array. We combine this data set with our high-spectral-resolution observations of the N, J = 2, 3∕2 → 1, 1∕2 transitions of CH near 149 μm observed towards the same sources made with the upGREAT receiver on SOFIA, which share common lower energy levels with the HFS transitions within the rotational ground state. Results. Towards all four sources, we observe the 3.264 GHz lower satellite line in enhanced emission with a higher relative intensity than is expected at LTE, by a factor of between 4 and 20. Employing recently calculated collisional rate coefficients, we perform statistical equilibrium calculations with the non-LTE radiative-transfer code MOLPOP-CEP in order to model the excitation conditions traced by the ground-state HFS lines of CH and to infer the physical conditions in the emitting regions. The models account for effects of far-infrared line overlap with additional constraints provided by reliable column densities of CH estimated from the 149 μm lines. Conclusions. The derived gas densities indicate that the CH radio emission lines (and the far-infrared absorption) arise from the diffuse and translucent outer regions of the envelopes of the SFRs as well as in such clouds located along the lines of sight. We infer temperatures ranging from 50 to 125 K. These elevated temperatures, together with astrochemical considerations, may indicate that CH is formed in material heated by the dissipation of interstellar turbulence, which has been invoked for other molecules. The excitation conditions we derive reproduce the observed level inversion in all three of the ground-state HFS lines of CH over a wide range of gas densities with an excitation temperature of ~−0.3 K, consistent with previous theoretical predictions.

Hunting for the elusive methylene radical

Context. The NKaKc = 404−313 transitions of ortho-CH2 between 68 and 71 GHz were first detected toward the Orion-KL and W51 Main star-forming regions. Given their high upper level energies (225 K) above the ground state, they were naturally thought to arise in dense, hot molecular cores near newly formed stars. However, this has not been confirmed by further observations of these lines and their origin has remained unclear. Generally, there is a scarcity of observational data for CH2 and, while it is an important compound in the astrochemical context, its actual occurrence in astronomical sources is poorly constrained. Aims. In this work, we aim to investigate the nature of the elusive CH2 emission, address its association with hot cores, and examine alternative possibilities for its origin. Owing to its importance in carbon chemistry, we also extend the search for CH2 lines by observing an assortment of regions, guided by the hypothesis that the observed CH2 emission is likely to arise from the hot gas environment of photodissociation regions (PDRs). Methods. We carried out our observations first using the Kitt Peak 12 m telescope to verify the original detection of CH2 toward different positions in the central region of the Orion Molecular Cloud 1. These were followed-up by deep integrations using the higher angular resolution of the Onsala 20 m telescope. We also searched for the NKaKc = 212−303 transitions of para-CH2 between 440–445 GHz toward the Orion giant molecular cloud complex using the APEX 12 m telescope. We also obtained auxiliary data for carbon recombination lines with the Effelsberg 100 m telescope and employing archival far infrared data. Results. The present study, along with other recent observations of the Orion region reported here, rule out the possibility of an association with gas that is both hot and dense. We find that the distribution of the CH2 emission closely follows that of the [CII] 158 μm emission, while CH2 is undetected toward the hot core itself. The observations suggest, rather, that its extended emission arises from hot but dilute layers of PDRs and not from the denser parts of such regions as in the case of the Orion Bar. This hypothesis was corroborated by comparisons of the observed CH2 line profiles with those of carbon radio recombination lines (CRRLs), which are well-known PDR tracers. In addition, we report the detection of the 70 GHz fine- and hyperfine structure components of ortho-CH2 toward the W51 E, W51 M, W51 N, W49 N, W43, W75 N, DR21, and S140 star-forming regions, and three of the NKaKc = 404−313 fine- and hyperfine structure transitions between 68–71 GHz toward W3 IRS5. While we have no information on the spatial distribution of CH2 in these regions, aside from that in W51, we again see a correspondence between the profiles of CH2 lines and those of CRRLs. We see a stronger CH2 emission toward the extended HII region W51 M rather than toward the much more massive and denser W51 E and N regions, which strongly supports the origin of CH2 in extended dilute gas. We also report the non-detection of the 212−303 transitions of para-CH2 toward Orion. Furthermore, using a non-LTE radiative transfer analysis, we can constrain the gas temperatures and H2 density to (163 ± 26) K and (3.4 ± 0.3) × 103 cm−3, respectively, for the 68–71 GHz ortho-CH2 transitions toward W3 IRS5, for which we have a data set of the highest quality. This analysis confirms our hypothesis that CH2 originates inwarm and dilute PDR layers. Our analysis suggests that for the excitation conditions under the physical conditions that prevail in such an environment, these lines are masering, with weak level inversion. The resulting amplification of the lines’ spontaneousemission greatly aids in their detection.

Hyperfine structure and electric quadrupole transitions in the deuterium molecular ion

Molecular hydrogen ions are of metrological relevance due to the possibility of precise theoretical evaluation of their spectrum and of external-field-induced shifts. In homonuclear molecular ions, the electric dipole $E1$ transitions are strongly suppressed, and of primary laser spectroscopy interest is the electric quadrupole ($E2$) transition spectrum. In continuation of previous work on the ${{\mathrm{H}}_{2}}^{+}$ ion, we report here the results of the calculations of the hyperfine structure of the laser-induced electric quadrupole transitions between a large set of rovibrational states of ${{\mathrm{D}}_{2}}^{+}$; the inaccuracies of previous evaluations have been corrected. The effects of the laser polarization are studied in detail. We show that the electric quadrupole moment of the deuteron can in principle be determined with low fractional uncertainty $(\ensuremath{\simeq}1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4})$ by comparing the results presented here with future data from precision spectroscopy of ${{\mathrm{D}}_{2}}^{+}$.

ATLASGAL – relationship between dense star-forming clumps and interstellar masers

ABSTRACT We have used catalogues from several Galactic plane surveys and dedicated observations to investigate the relationship between various maser species and Galactic star-forming clumps, as identified by the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) survey. The maser transitions of interest are the 6.7 and 12.2-GHz methanol masers, 22.2-GHz water masers, and the masers emitting in the four ground-state hyperfine structure transitions of hydroxyl. We find clump association rates for the water, hydroxyl and methanol masers to be 56, 39, and 82 per cent, respectively, within the Galactic longitude range of 60○ > ℓ > −60○. We investigate the differences in physical parameters between maser associated clumps and the full ATLASGAL sample, and find that clumps coincident with maser emission are more compact with increased densities and luminosities. However, we find the physical conditions within the clumps are similar for the different maser species. A volume density threshold of n(H2) > 104.1 cm−3 for the 6.7-GHz methanol maser found in our previous study is shown to be consistent across for all maser species investigated. We find limits that are required for the production of maser emission to be 500 L⊙ and 6 M⊙, respectively. The evolutionary phase of maser associated clumps is investigated using the L/M ratio of clumps coincident with maser emission, and these have similar L/M ranges (∼100.2−102.7 L⊙/M⊙) regardless of the associated transitions. This implies that the conditions required for the production of maser emission only occur during a relatively narrow period during a star’s evolution. Lower limits of the statistical lifetimes for each maser species are derived, ranging from ∼0.4−2 × 104 yr and are in good agreement with the ‘straw man’ evolutionary model previously presented.

Importance of Angle-dependent Partial Frequency Redistribution in Hyperfine Structure Transitions Under the Incomplete Paschen–Back Effect Regime

Abstract Angle-frequency coupling in scattering of polarized light on atoms is represented by the angle-dependent (AD) partial frequency redistribution (PRD) matrices. There are several lines in the linearly polarized solar spectrum, for which PRD combined with quantum interference between hyperfine structure states play a significant role. Here we present the solution of the polarized line transfer equation including the AD-PRD matrix for scattering on a two-level atom with hyperfine structure splitting and an unpolarized lower level. We account for the effects of arbitrary magnetic fields (including the incomplete Paschen–Back effect regime) and elastic collisions. For exploratory purposes we consider a self-emitting isothermal planar atmosphere and use atomic parameters that represent an isolated Na i D2 line. For this case we show that the AD-PRD effects are significant for field strengths below about 30 G, but that the computationally much less demanding approximation of angle-averaged PRD may be used for stronger fields.

The excitation temperature of the CH 3335-MHz line

ABSTRACT Molecular hydrogen is the main constituent of dense molecular clouds, but is expected to also be a dominant constituent in many environments where CO can no longer be seen, the so-called ‘CO-dark molecular gas’. Based on comparisons of ultraviolet spectroscopy of H2 and optical line observations (4300 Å), CH is a prime candidate to trace H2. Since the optical line (and the UV lines at 3143, 3890, and 3878 Å) require bright background sources (and the CH N = 2←1 ground state rotation line at 149 µm requires space-based, or stratospheric, observations), the hyperfine structure transition at 3335 MHz is a potentially important tool for probing the CO-dark molecular gas. However, the excitation of this transition is complicated, and has often been found to be inverted, making column density determinations uncertain. To clarify the potential use of the 3.3-GHz line as a proxy for H2, we have observed the CH 3335-MHz line with the Arecibo 305-m radio telescope along 16 lines of sight towards stars with existing measurements of the 4300-Å line. By comparing the CH column densities from optical and UV absorption lines to the CH radio emission line, we can derive the excitation temperature (Tex) of the 3335-MHz transition. We obtain a wide range of excitation temperatures for nine lines of sight, including some with |Tex| < 5 K. The common assumption that Tex for the 3335-MHz line is always much larger than the background temperature (Tbg) is not always warranted and can lead to significant errors in the value of N(CH).

Theoretical study of the spectroscopic properties of mendelevium ([formula omitted

Using recently developed version of the configuration interaction method for atoms with open shells we calculate the spectroscopic properties of the mendelevium atom (Md, Z=101). These include energy levels, first and second ionisation potentials, electron affinities, hyperfine structure and electric dipole transition amplitudes between ground and low lying states of opposite parity. The accuracy of the calculations is controlled by performing similar calculations for a lighter homolog of mendelevium, the thulium atom and comparing the results with experiments and other calculations. The calculations for Md are to address the lack of experimental data and help in planning and interpreting the measurements.

RELATIVISTIC THEORY OF SPECTRA OF PIONIC AND KAONIC ATOMS: HYPERFINE STRUCTURE, TRANSITION PROBABILITIES FOR NITROGEN

A new theoretical approach to energy and spectral parameters of the hadronic (pionic and kaonic) atoms in the excited states with precise accounting for the relativistic, radiation and nuclear effects is applied to the study of radiation parameters of transitions between hyperfine structure components of the pionic and kaonic nitrogen. The advanced data on the probabilities of radiation transitions between components of the hyperfine structure transitions 5g-4f, 5f-4d in the spectrum of pionic nitrogen and 8k-7i, 8i-7h in the spectrum of kaonic nitrogen are presented and compared with alternative theoretical data.

Study of a Selective Photoionization Scheme of 177Lu

The hyperfine structure of transitions in the three-step scheme 5d6s22D3/2–5d6s6p4F $$_{{5/2}}^{^\circ }$$ –5d6s7s4D3/2– (53 375 cm–1) $$_{{1/2}}^{^\circ }$$ of lutetium ionization is studied for 175Lu, 176Lu, and 177Lu isotopes using the photoionization laser spectroscopy method. Values of the magnetic dipole (A) and electric quadrupole (B) interaction constants are determined, as well as the energies, the isotope shifts, and the radiative lifetimes for the 5d6s7s4D3/2 and (53 375 cm–1) $$_{{1/2}}^{^\circ }$$ levels.

RELATIVISTIC THEORY OF SPECTRA OF USUAL AND EXOTIC ATOMS: NITROGEN HYPERFINE TRANSITIONS ENERGIES

A new theoretical approach to the description of spectral parameters pionic atoms in the excited states with precise accounting relativistic, radiation and nuclear effects is applied to the study of energy and spectral parameters of transitions between hyperfine structure components. As an example of the present approach presents new data on the energies of the hyperfine structure transitions 5g4f, 5f-4d in the spectrum of pionic nitrogen are presented and it is performed comparison with the corresponding theoretical data by Trassinelli-Indelicato

Precision Muonium Spectroscopy

The muonium atom is the purely leptonic bound state of a positive muon and an electron. It has a lifetime of 2.2 µs. The absence of any known internal structure provides for precision experiments to test fundamental physics theories and to determine accurate values of fundamental constants. In particular ground state hyperfine structure transitions can be measured by microwave spectroscopy to deliver the muon magnetic moment. The frequency of the 1s–2s transition in the hydrogen-like atom can be determined with laser spectroscopy to obtain the muon mass. With such measurements fundamental physical interactions, in particular quantum electrodynamics, can also be tested at highest precision. The results are important input parameters for experiments on the muon magnetic anomaly. The simplicity of the atom enables further precise experiments, such as a search for muonium–antimuonium conversion for testing charged lepton number conservation and searches for possible antigravity of muons and dark matter.

RELATIVISTIC THEORY OF SPECTRA OF PIONIC ATOMS: RADIATION TRANSITION PROBABILITIES

A new theoretical approach to the description of spectral parameters pionic atoms in the excited states with precise accounting relativistic, radiation and nuclear effects is applied to the study of radiation parameters of transitions between hyperfine structure components. As an example of the present approach presents new data on the probabilities of radiation transitions between components of the hyperfine structure transitions 5g-4f, 5f-4d in the spectrum of pionic nitrogen are presented and it is performed comparison with the corresponding theoretical data by Trassinelli-Indelicato.

High-Resolution Spectroscopy on the Laser-Cooling CandidateLa−

The bound-bound transition from the 5d^{2}6s^{2} ^{3}F_{2}^{e} ground state to the 5d6s^{2}6p ^{3}D_{1}^{o} excited state in negative lanthanum has been proposed as a candidate for laser cooling, which has not yet been achieved for negative ions. Anion laser cooling holds the potential to allow the production of ultracold ensembles of any negatively charged species. We have studied the aforementioned transition in a beam of negative La ions by high-resolution laser spectroscopy. The center-of-gravity frequency was measured to be 96.592 80(10)THz. Seven of the nine expected hyperfine structure transitions were resolved. The observed peaks were unambiguously assigned to the predicted hyperfine transitions by a fit, confirmed by multiconfigurational self-consistent field calculations. From the determined hyperfine structure we conclude that La^{-} is a promising laser cooling candidate. Using this transition, only three laser beams would be required to repump all hyperfine levels of the ground state.

Energy, fine structure, hyperfine structure, and radiative transition rates of the high-lying multi-excited states for B-like neon

The Rayleigh-Ritz variational method with multiconfiguration interaction wave functions is used to obtain the energies of high-lying multi-excited quartet states 1s 22s2pnl and 1s 22p 2 nl 4Pe,o (n ≥ 2) in B-like neon, including the mass polarization and relativistic corrections. The fine structure and hyperfine structure of the excited quartet states for this system are investigated. Configuration structures of the high-lying multi-excited series are further identified by relativistic corrections and fine structure splittings. The transition rates and wavelengths are also calculated. Calculated wavelengths include the quantum electrodynamic effects. The results are compared with other theoretical and experimental data in the literature.

An atomic hydrogen beam to test ASACUSA’s apparatus for antihydrogen spectroscopy

The ASACUSA collaboration aims to measure the ground state hyperfine splitting (GS-HFS) of antihydrogen, the antimatter pendant to atomic hydrogen. Comparisons of the corresponding transitions in those two systems will provide sensitive tests of the CPT symmetry, the combination of the three discrete symmetries charge conjugation, parity, and time reversal. For offline tests of the GS-HFS spectroscopy apparatus we constructed a source of cold polarised atomic hydrogen. In these proceedings we report the successful observation of the hyperfine structure transitions of atomic hydrogen with our apparatus in the earth's magnetic field.

Laser spectroscopy of holmium monosulphide: Hyperfine structure in the A[14.79]8.5, X18.5, X27.5 and W17.5 states

Laser induced fluorescence spectra, using a single frequency ring dye laser, have shown hyperfine structure in transitions from the A[14.79]8.5 state of HoS to three low-lying electronic states, X18.5, X27.5 and W17.5. Analysis of the hyperfine structure yielded magnetic hyperfine parameters, h(X1)=0.3298(27)cm−1, h(X2)=0.1124(29)cm−1, h(W1)=0.275(5)cm−1 and h(A)=0.2314(25)cm−1. The three low lying states originate from the ground Ho2+{4f10(5I8)6s}S2− configuration and the hyperfine parameters were used to determine the free Ho2+ ion quantum numbers appropriate to each state as well as the approximate relative contributions of the 4f and 6s electrons to the overall hyperfine energy. Calculation of the ground state magnetic hyperfine parameter h(X18.5) from atomic hyperfine parameters was found to be consistent with the observed values.

Spontaneous decay rates of the hyperfine structure atomic states into an optical nanofiber

Spontaneous decay rates of atoms into guided modes of an optical nanofiber are found for atomic transitions between the hyperfine structure sublevels. The decay rates are evaluated for the hyperfine structure transitions in Rb atoms. The efficiency of the guided mode excitation by spontaneous decay of the specific hyperfine atomic states is examined for both the fundamental fiber mode HE11 and the higher-order modes TE01, TM01, and HE21.

CN excitation and electron densities in diffuse molecular clouds

Utilising previous work by the authors on the spin-coupled rotational cross-sections for electron-CN collisions, data for the associated rate coefficients is presented. Data on rotational, fine-structure and hyperfine-structure transition involving rotational levels up to $N$=20 are computed for temperatures in the range 10 -- 1000~K. Rates are calculated by combining Born-corrected R-matrix calculations with the infinite-order-sudden (IOS) approximation. The dominant hyperfine transitions are those with $\Delta N=\Delta j= \Delta F=1$. For dipole-allowed transitions, electron-impact rates are shown to exceed those for excitation of CN by para-H$_2$($j=0$) by five orders of magnitude. The role of electron collisions in the excitation of CN in diffuse clouds, where local excitation competes with the cosmic microwave background (CMB) photons, is considered. Radiative transfer calculations are performed and the results compared to observations. These comparisons suggest that electron density lies in the range $n(e)\sim 0.01-0.06$~cm$^{-3}$ for typical physical conditions present in diffuse clouds.