Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical Review B

Spectroscopy of Yb 3 + : CaF 2 : From isolated centers to clusters

Vincent Petit, Patrice Camy, Jean‐Louis Doualan, X. Portier, R. Moncorgé

Published Aug 27, 2008• 143 citations
Publisher

Abstract

A detailed spectroscopic study of ${\text{Yb}}^{3+}:{\text{CaF}}_{2}$ is made by using laser selective excitation, low-temperature time-resolved fluorescence, and Raman techniques. Three dominant types of ${\text{Yb}}^{3+}$ isolated ion centers are identified at very low $(0.03\text{ }\text{at}\text{.}\text{ }%)$ dopant concentration: two of them with cubic and tetragonal symmetries and the third one not clearly identified but likely of trigonal symmetry. Fluorescence decays strongly differ from one site to another. The overall measured positions of the Stark sublevels of the ${^{2}F}_{7/2}$ and ${^{2}F}_{5/2}$ multiplets are satisfactorily explained by the crystal-field calculations. On the other hand, at higher dopant concentrations, only one dominant class of ${\text{Yb}}^{3+}$ centers occurs which corresponds to some hexameric cluster in which the ${\text{Yb}}^{3+}$ ions site in nearly tetragonal crystal-field environments and whose energy-level positions are discussed and compared with those previously reported in the literature.

DOI
10.1103/physrevb.78.085131

Related papers

Site-selective spectroscopy of Ho3+ ions in CsCdBr3 crystals

Marjorie Mujaji, Glynn D. Jones, R. W. G. Syme

With the use of laser-selective excitation, an extensive set of energy levels has been established for the principal ${\mathrm{Ho}}^{3+}$ dimer center in ${\mathrm{CsCdBr}}_{3}$:${\mathrm{Ho}}^{3+}$ crystals. The observed splittings of around 2 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ of the transitions to or from energy levels assigned as having ${\ensuremath{\gamma}}_{3}$ symmetry under ${\mathit{C}}_{3\mathit{v}}$ symmetry is indicative of deviations of the ${\mathrm{Ho}}^{3+}$ ion-site symmetry from exact ${\mathrm{C}}_{3\mathit{v}}$ symmetry. As for the previously studied ${\mathrm{Er}}^{3+}$ pair center in ${\mathrm{CsCdBr}}_{3}$, the ${\mathrm{Ho}}^{3+}$ pair center exhibits strong upconversion fluorescence with up to one-third the intensity of the direct fluorescence under cw laser excitation of the $^{5}$${\mathit{I}}_{8}$${\ensuremath{\rightarrow}}^{5}$${\mathit{S}}_{2}$ transition in the green and up to one-fifteenth the intensity for comparable cw laser excitation of the $^{5}$${\mathit{I}}_{8}$${\ensuremath{\rightarrow}}^{5}$${\mathit{F}}_{5}$ transition in the red. Additional small splittings of up to 0.5 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ appear for the sharper transitions and are attributed to the ion-pair interaction. Energy levels are also reported for three varieties of minority centers with one of these centers being present in both 0.3% and 0.1% ${\mathrm{Ho}}^{3+}$ crystals, another in 0.01% ${\mathrm{Ho}}^{3+}$ crystals and the third in ${\mathrm{Na}}^{+}$ codoped crystals. Crystal-field analyses are reported for the principal dimer center and two of the minority centers. Fluorescence lifetimes were determined for several transitions of the dimer center and used to infer energy-transfer rates. Preliminary high-resolution results are reported for the excitation profiles of the two lowest-energy $^{5}$${\mathit{I}}_{8}$${\ensuremath{\rightarrow}}^{5}$${\mathit{F}}_{5}$ transitions that show complex hyperfine patterns.

Physical review. B, Condensed matter•Jul 1, 1993•36 citations

Spectroscopy, Crystal-Field, and Transition Intensity Analyses of the C$_{\rm 3v}$(O$^{2-}$) Centre in Er$^{3+}$ Doped CaF$_{2}$ Crystals

M. D. Moull, Jamin L.B. Martin, Newman, T. G. M. +4 more

Erbium ions in crystals show considerable promise for the technologies that will form the backbone of future networked quantum information technology. Despite advances in leveraging erbium's fibre-compatible infrared transition for classical and quantum applications, the transitions are, in general, not well understood. We present detailed absorption and laser site-selective spectroscopy of the C$_{\rm 3v}$(O$^{2-}$) centre in CaF$_2$:Er$^{3+}$ as an interesting erbium site case study. The $^{4}$I$_{15/2}$Z$_1 \rightarrow {^{4}}$I$_{13/2}$Y$_1$ transition has a low-temperature inhomogeneous linewidth of 1 GHz with hyperfine structure observable from the $^{167}$Er isotope. A parametrized crystal-field Hamiltonian is fitted to 34 energy levels and the two ground state magnetic splitting factors. The wavefunctions are used to perform a transition intensity analysis and electric-dipole parameters are fitted to absorption oscillator strengths. Simulated spectra for the $^{4}$I$_{11/2}\rightarrow {^{4}}$I$_{15/2}$ and $^{4}$I$_{13/2} \rightarrow {^{4}}$I$_{15/2}$ inter-multiplet transitions are in excellent agreement with the experimentally measured spectra. The $^{4}$I$_{13/2}$ excited state lifetime is 25.0\,ms and the intensity calculation is in excellent agreement with this value.

arXiv:2409.15622•Sep 23, 2024•0 citations

Site-selective laser spectroscopy of Pr3+ C4v symmetry centers in hydrogenated CaF2 : Pr3+ and SrF2 : Pr3+ crystals

Roger J. Reeves, Glynn D. Jones, R. W. G. Syme

Laser-selective excitation and optical-absorption techniques have been used to establish comprehensive sets of energy levels for both the ${\mathit{F}}^{\mathrm{\ensuremath{-}}}$ and hydrogenic varieties of the tetragonal symmetry (${\mathit{C}}_{4\mathit{v}}$) centers in ${\mathrm{SrF}}_{2}$ and ${\mathrm{CaF}}_{2}$. Polarization of the various spectral lines was used to determine the symmetry labels of many of the energy levels. Reversals of the ordering of some levels between ${\mathrm{SrF}}_{2}$ and ${\mathrm{CaF}}_{2}$ are found and, in particular, the two lowest levels (${\mathit{D}}_{1}$ and ${\mathit{D}}_{2}$) of the $^{1}$${\mathit{D}}_{2}$ multiplet, which are the originating levels for many of the observed emission transitions, have reversed-symmetry label assignments in ${\mathrm{SrF}}_{2}$ and ${\mathrm{CaF}}_{2}$. Differences were found between the ground-state Zeeman splittings for the ${\mathit{C}}_{4\mathit{v}}$ ${\mathit{F}}^{\mathrm{\ensuremath{-}}}$ and ${\mathit{D}}^{\mathrm{\ensuremath{-}}}$ centers for both ${\mathrm{SrF}}_{2}$ and ${\mathrm{CaF}}_{2}$. Fluorescence lifetimes of the ${\mathit{C}}_{4\mathit{v}}$ hydrogenic centers show a strong dependence on the particular charge-compensating ion present through nonradiative decay processes involving the respective local mode phonons. The upconversion spectra observed for ${\mathit{F}}^{\mathrm{\ensuremath{-}}}$, ${\mathit{T}}^{\mathrm{\ensuremath{-}}}$, and ${\mathit{D}}^{\mathrm{\ensuremath{-}}}$ varieties of the ${\mathit{C}}_{4\mathit{v}}$ centers in ${\mathrm{SrF}}_{2}$ and for the ${\mathit{C}}_{4\mathit{v}}$ ${\mathit{F}}^{\mathrm{\ensuremath{-}}}$ center in ${\mathrm{CaF}}_{2}$ are all consistent with excitation of specific subsets of nearby ${\mathit{C}}_{4\mathit{v}}$ centers.

Physical review. B, Condensed matter•Sep 1, 1992•34 citations

Spectroscopy, crystal-field, and transition intensity analyses of the C 3v (O 2− ) centre in Er 3+ doped CaF2 crystals

M. D. Moull, Jamin L.B. Martin, T.G.M. Newman +4 more

Erbium ions in crystals show considerable promise for the technologies that will form the backbone of future networked quantum information technology. Despite advances in leveraging erbium’s fibre-compatible infrared transition for classical and quantum applications, the transitions are, in general, not well understood. We present detailed absorption and laser site-selective spectroscopy of the C 3v (O 2 − ) centre in CaF 2 :Er 3 + as an interesting erbium site case study. The 4 I 15 / 2 Z 1 → 4 I 13 / 2 Y 1 transition has a low-temperature inhomogeneous linewidth of 1 GHz with hyperfine structure observable from the 167 Er isotope. A parametrized crystal-field Hamiltonian is fitted to 34 energy levels and the two ground state magnetic splitting factors. The wavefunctions are used to perform a transition intensity analysis and electric-dipole parameters are fitted to absorption oscillator strengths. Simulated spectra for the 4 I 11 / 2 → 4 I 15 / 2 and 4 I 13 / 2 → 4 I 15 / 2 inter-multiplet transitions are in excellent agreement with the experimentally measured spectra. The 4 I 13 / 2 excited state lifetime is 25.0 ms and the intensity calculation is in excellent agreement with this value. • Detailed spectroscopic study of the C 3v (O 2 − ) Centre in CaF 2 :Er 3 + . • Crystal-field fit to 34 energy levels and ground-state magnetic splitting. • Transition intensity analysis for the technologically relevant infrared transitions.

Optical Materials X•Sep 27, 2024•1 citation

Spectroscopy and Optical Maser Action in Sr F2 : Sm2+

P. P. Sorokin, M. J. Stevenson, J. R. Lankard +1 more

A crystal of Sr${\mathrm{F}}_{2}$: ${\mathrm{Sm}}^{2+}$ was operated as a pulsed optical maser at temperatures close to 4.2\ifmmode^\circ\else\textdegree\fi{}K. The 6969 \AA{} output corresponds to the wavelength of an exceedingly sharp line ($\ensuremath{\Delta}\ensuremath{\nu}<0.6$ ${\mathrm{cm}}^{\ensuremath{-}1}$) in which almost all of the low-temperature fluorescence is concentrated. In contrast to what prevails in Ca${\mathrm{F}}_{2}$: ${\mathrm{Sm}}^{+2}$ masers, the output is characterized by strong relaxation oscillations. This may be explained by the large difference in the fluorescent lifetimes in the two systems. While in Ca${\mathrm{F}}_{2}$: ${\mathrm{Sm}}^{2+}$ the value of $\ensuremath{\tau}$ is approximately 1.5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}6}$ sec, in Sr${\mathrm{F}}_{2}$: ${\mathrm{Sm}}^{2+}$ it has a value of 15 msec. The reason for the large difference in $\ensuremath{\tau}$ values, in turn, depends upon the relative proximity of the long-wavelength edge of the red band to the position of the metastable $^{5}D_{0}$ level from which fluorescence occurs. Absorption measurements taken at helium temperatures on Sr${\mathrm{F}}_{2}$: ${\mathrm{Sm}}^{2+}$ show that the lowest vibrational level of the lowest lying $4f\ensuremath{-}5d$ band lies \ensuremath{\sim}600 ${\mathrm{cm}}^{\ensuremath{-}1}$ above the position of the $^{5}D_{0}$ level while in Ca${\mathrm{F}}_{2}$: ${\mathrm{Sm}}^{2+}$ there is near coincidence of the corresponding levels and consequently strong configurational mixing. Crystals of Sr${\mathrm{Cl}}_{2}$: ${\mathrm{Sm}}^{2+}$ were also studied in this regard and display an expected close similarity in spectral characteristics to Sr${\mathrm{F}}_{2}$: ${\mathrm{Sm}}^{2+}$. The vibrational structure on the $4f\ensuremath{-}5d$ bands is much more pronounced, however, than in Ca${\mathrm{F}}_{2}$: ${\mathrm{Sm}}^{2+}$ and Sr${\mathrm{F}}_{2}$: ${\mathrm{Sm}}^{2+}$, indicating weaker coupling to the lattice in the excited $5d$ state. A tentative interpretation for the splitting of the red band seen in the absorption spectra of ${\mathrm{Sm}}^{2+}$ ions is given.

Physical Review•Jul 15, 1962•66 citations

High-resolution spectroscopy of neutral Yb atoms in a solid Ne matrix

Ricardo Lewis Lambo, Chenyu Xu, S. T. Pratt +11 more

We present an experimental and theoretical study of the absorption and emission spectra of Yb atoms in a solid Ne matrix at a resolution of 0.025 nm. Five absorption bands were identified as due to transitions from the $4{f}^{14}5{d}^{0}6{s}^{2}{\phantom{\rule{4pt}{0ex}}}^{1}{S}_{0}$ ground-state configuration to $4{f}^{14}5{d}^{0}6s6p$ and $4{f}^{13}5{d}^{1}6{s}^{2}$ configurations. The two lowest-energy bands were assigned to outer-shell transitions to $6s6p{\phantom{\rule{4pt}{0ex}}}^{3}{P}_{1}$ and ${}^{1}{P}_{1}$ atomic states and displayed the structure of a broad doublet and an asymmetric triplet, respectively. The remaining three higher-frequency bands were assigned to inner-shell transitions to distinct $J=1$ states arising from the $4{f}^{13}5{d}^{1}6{s}^{2}$ configuration and were highly structured with narrow linewidths. A classical simulation was performed to identify the stability and symmetry of possible trapping sites in the Ne crystal. It showed that the overarching $1+2$ structure of the high-frequency bands could be predominantly ascribed to crystal-field splitting in the axial field of a 10-atom vacancy of ${C}_{4v}$ symmetry. Their prominent substructures were shown to be manifestations of phonon sidebands associated with the zero-phonon lines on each crystal-field state. Unprecedented for a metal--rare-gas system, resolution of individual phonon states on an allowed electronic transition was possible under excitation spectroscopy which reflects the semiquantum nature of solid Ne. In contrast to the absorption spectra, emission spectra produced by steady-state excitation into the ${}^{1}{P}_{1}$ absorption band consisted of simple, unstructured fluorescence bands.

arXiv:2107.04186•Physical Review A•Dec 16, 2021•8 citations
A detailed spectroscopic study of Yb3+:CaF2{\text{Yb}}^{3+}:{\text{CaF}}_{2}Yb3+:CaF2​ is made by using laser selective excitation, low-temperature time-resolved fluorescence, and Raman techniques. Three dominant types of Yb3+{\text{Yb}}^{3+}Yb3+ isolated ion centers are identified at very low (0.03 at. (0.03\text{ }\text{at}\text{.}\text{ }%)(0.03 at.  dopant concentration: two of them with cubic and tetragonal symmetries and the third one not clearly identified but likely of trigonal symmetry. Fluorescence decays strongly differ from one site to another. The overall measured positions of the Stark sublevels of the 2F7/2{^{2}F}_{7/2}2F7/2​ and 2F5/2{^{2}F}_{5/2}2F5/2​ multiplets are satisfactorily explained by the crystal-field calculations. On the other hand, at higher dopant concentrations, only one dominant class of Yb3+{\text{Yb}}^{3+}Yb3+ centers occurs which corresponds to some hexameric cluster in which the Yb3+{\text{Yb}}^{3+}Yb3+ ions site in nearly tetragonal crystal-field environments and whose energy-level positions are discussed and compared with those previously reported in the literature.
With the use of laser-selective excitation, an extensive set of energy levels has been established for the principal Ho3+{\mathrm{Ho}}^{3+}Ho3+ dimer center in CsCdBr3{\mathrm{CsCdBr}}_{3}CsCdBr3​:Ho3+{\mathrm{Ho}}^{3+}Ho3+ crystals. The observed splittings of around 2 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ of the transitions to or from energy levels assigned as having ${\ensuremath{\gamma}}_{3}$ symmetry under C3v{\mathit{C}}_{3\mathit{v}}C3v​ symmetry is indicative of deviations of the Ho3+{\mathrm{Ho}}^{3+}Ho3+ ion-site symmetry from exact C3v{\mathrm{C}}_{3\mathit{v}}C3v​ symmetry. As for the previously studied Er3+{\mathrm{Er}}^{3+}Er3+ pair center in CsCdBr3{\mathrm{CsCdBr}}_{3}CsCdBr3​, the Ho3+{\mathrm{Ho}}^{3+}Ho3+ pair center exhibits strong upconversion fluorescence with up to one-third the intensity of the direct fluorescence under cw laser excitation of the 5^{5}5I8{\mathit{I}}_{8}I8​${\ensuremath{\rightarrow}}^{5}$S2{\mathit{S}}_{2}S2​ transition in the green and up to one-fifteenth the intensity for comparable cw laser excitation of the 5^{5}5I8{\mathit{I}}_{8}I8​${\ensuremath{\rightarrow}}^{5}$F5{\mathit{F}}_{5}F5​ transition in the red. Additional small splittings of up to 0.5 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ appear for the sharper transitions and are attributed to the ion-pair interaction. Energy levels are also reported for three varieties of minority centers with one of these centers being present in both 0.3% and 0.1% Ho3+{\mathrm{Ho}}^{3+}Ho3+ crystals, another in 0.01% Ho3+{\mathrm{Ho}}^{3+}Ho3+ crystals and the third in Na+{\mathrm{Na}}^{+}Na+ codoped crystals. Crystal-field analyses are reported for the principal dimer center and two of the minority centers. Fluorescence lifetimes were determined for several transitions of the dimer center and used to infer energy-transfer rates. Preliminary high-resolution results are reported for the excitation profiles of the two lowest-energy 5^{5}5I8{\mathit{I}}_{8}I8​${\ensuremath{\rightarrow}}^{5}$F5{\mathit{F}}_{5}F5​ transitions that show complex hyperfine patterns.
Spectroscopy, Crystal-Field, and Transition Intensity Analyses of the C3v_{\rm 3v}3v​(O2−^{2-}2−) Centre in Er3+^{3+}3+ Doped CaF2_{2}2​ Crystals
Erbium ions in crystals show considerable promise for the technologies that will form the backbone of future networked quantum information technology. Despite advances in leveraging erbium's fibre-compatible infrared transition for classical and quantum applications, the transitions are, in general, not well understood. We present detailed absorption and laser site-selective spectroscopy of the C3v_{\rm 3v}3v​(O2−^{2-}2−) centre in CaF2_22​:Er3+^{3+}3+ as an interesting erbium site case study. The 4^{4}4I15/2_{15/2}15/2​Z1→4_1 \rightarrow {^{4}}1​→4I13/2_{13/2}13/2​Y1_11​ transition has a low-temperature inhomogeneous linewidth of 1 GHz with hyperfine structure observable from the 167^{167}167Er isotope. A parametrized crystal-field Hamiltonian is fitted to 34 energy levels and the two ground state magnetic splitting factors. The wavefunctions are used to perform a transition intensity analysis and electric-dipole parameters are fitted to absorption oscillator strengths. Simulated spectra for the 4^{4}4I11/2→4_{11/2}\rightarrow {^{4}}11/2​→4I15/2_{15/2}15/2​ and 4^{4}4I13/2→4_{13/2} \rightarrow {^{4}}13/2​→4I15/2_{15/2}15/2​ inter-multiplet transitions are in excellent agreement with the experimentally measured spectra. The 4^{4}4I13/2_{13/2}13/2​ excited state lifetime is 25.0\,ms and the intensity calculation is in excellent agreement with this value.
Laser-selective excitation and optical-absorption techniques have been used to establish comprehensive sets of energy levels for both the ${\mathit{F}}^{\mathrm{\ensuremath{-}}}$ and hydrogenic varieties of the tetragonal symmetry (C4v{\mathit{C}}_{4\mathit{v}}C4v​) centers in SrF2{\mathrm{SrF}}_{2}SrF2​ and CaF2{\mathrm{CaF}}_{2}CaF2​. Polarization of the various spectral lines was used to determine the symmetry labels of many of the energy levels. Reversals of the ordering of some levels between SrF2{\mathrm{SrF}}_{2}SrF2​ and CaF2{\mathrm{CaF}}_{2}CaF2​ are found and, in particular, the two lowest levels (D1{\mathit{D}}_{1}D1​ and D2{\mathit{D}}_{2}D2​) of the 1^{1}1D2{\mathit{D}}_{2}D2​ multiplet, which are the originating levels for many of the observed emission transitions, have reversed-symmetry label assignments in SrF2{\mathrm{SrF}}_{2}SrF2​ and CaF2{\mathrm{CaF}}_{2}CaF2​. Differences were found between the ground-state Zeeman splittings for the C4v{\mathit{C}}_{4\mathit{v}}C4v​ ${\mathit{F}}^{\mathrm{\ensuremath{-}}}$ and ${\mathit{D}}^{\mathrm{\ensuremath{-}}}$ centers for both SrF2{\mathrm{SrF}}_{2}SrF2​ and CaF2{\mathrm{CaF}}_{2}CaF2​. Fluorescence lifetimes of the C4v{\mathit{C}}_{4\mathit{v}}C4v​ hydrogenic centers show a strong dependence on the particular charge-compensating ion present through nonradiative decay processes involving the respective local mode phonons. The upconversion spectra observed for ${\mathit{F}}^{\mathrm{\ensuremath{-}}}$, ${\mathit{T}}^{\mathrm{\ensuremath{-}}}$, and ${\mathit{D}}^{\mathrm{\ensuremath{-}}}$ varieties of the C4v{\mathit{C}}_{4\mathit{v}}C4v​ centers in SrF2{\mathrm{SrF}}_{2}SrF2​ and for the C4v{\mathit{C}}_{4\mathit{v}}C4v​ ${\mathit{F}}^{\mathrm{\ensuremath{-}}}$ center in CaF2{\mathrm{CaF}}_{2}CaF2​ are all consistent with excitation of specific subsets of nearby C4v{\mathit{C}}_{4\mathit{v}}C4v​ centers.
Erbium ions in crystals show considerable promise for the technologies that will form the backbone of future networked quantum information technology. Despite advances in leveraging erbium’s fibre-compatible infrared transition for classical and quantum applications, the transitions are, in general, not well understood. We present detailed absorption and laser site-selective spectroscopy of the C 3v (O 2 − ) centre in CaF 2 :Er 3 + as an interesting erbium site case study. The 4 I 15 / 2 Z 1 → 4 I 13 / 2 Y 1 transition has a low-temperature inhomogeneous linewidth of 1 GHz with hyperfine structure observable from the 167 Er isotope. A parametrized crystal-field Hamiltonian is fitted to 34 energy levels and the two ground state magnetic splitting factors. The wavefunctions are used to perform a transition intensity analysis and electric-dipole parameters are fitted to absorption oscillator strengths. Simulated spectra for the 4 I 11 / 2 → 4 I 15 / 2 and 4 I 13 / 2 → 4 I 15 / 2 inter-multiplet transitions are in excellent agreement with the experimentally measured spectra. The 4 I 13 / 2 excited state lifetime is 25.0 ms and the intensity calculation is in excellent agreement with this value. • Detailed spectroscopic study of the C 3v (O 2 − ) Centre in CaF 2 :Er 3 + . • Crystal-field fit to 34 energy levels and ground-state magnetic splitting. • Transition intensity analysis for the technologically relevant infrared transitions.
A crystal of SrF2{\mathrm{F}}_{2}F2​: Sm2+{\mathrm{Sm}}^{2+}Sm2+ was operated as a pulsed optical maser at temperatures close to 4.2\ifmmode^\circ\else\textdegree\fi{}K. The 6969 \AA{} output corresponds to the wavelength of an exceedingly sharp line ($\ensuremath{\Delta}\ensuremath{\nu}<0.6$ ${\mathrm{cm}}^{\ensuremath{-}1}$) in which almost all of the low-temperature fluorescence is concentrated. In contrast to what prevails in CaF2{\mathrm{F}}_{2}F2​: Sm+2{\mathrm{Sm}}^{+2}Sm+2 masers, the output is characterized by strong relaxation oscillations. This may be explained by the large difference in the fluorescent lifetimes in the two systems. While in CaF2{\mathrm{F}}_{2}F2​: Sm2+{\mathrm{Sm}}^{2+}Sm2+ the value of $\ensuremath{\tau}$ is approximately 1.5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}6}$ sec, in SrF2{\mathrm{F}}_{2}F2​: Sm2+{\mathrm{Sm}}^{2+}Sm2+ it has a value of 15 msec. The reason for the large difference in $\ensuremath{\tau}$ values, in turn, depends upon the relative proximity of the long-wavelength edge of the red band to the position of the metastable 5D0^{5}D_{0}5D0​ level from which fluorescence occurs. Absorption measurements taken at helium temperatures on SrF2{\mathrm{F}}_{2}F2​: Sm2+{\mathrm{Sm}}^{2+}Sm2+ show that the lowest vibrational level of the lowest lying $4f\ensuremath{-}5d$ band lies \ensuremath{\sim}600 ${\mathrm{cm}}^{\ensuremath{-}1}$ above the position of the 5D0^{5}D_{0}5D0​ level while in CaF2{\mathrm{F}}_{2}F2​: Sm2+{\mathrm{Sm}}^{2+}Sm2+ there is near coincidence of the corresponding levels and consequently strong configurational mixing. Crystals of SrCl2{\mathrm{Cl}}_{2}Cl2​: Sm2+{\mathrm{Sm}}^{2+}Sm2+ were also studied in this regard and display an expected close similarity in spectral characteristics to SrF2{\mathrm{F}}_{2}F2​: Sm2+{\mathrm{Sm}}^{2+}Sm2+. The vibrational structure on the $4f\ensuremath{-}5d$ bands is much more pronounced, however, than in CaF2{\mathrm{F}}_{2}F2​: Sm2+{\mathrm{Sm}}^{2+}Sm2+ and SrF2{\mathrm{F}}_{2}F2​: Sm2+{\mathrm{Sm}}^{2+}Sm2+, indicating weaker coupling to the lattice in the excited 5d5d5d state. A tentative interpretation for the splitting of the red band seen in the absorption spectra of Sm2+{\mathrm{Sm}}^{2+}Sm2+ ions is given.
We present an experimental and theoretical study of the absorption and emission spectra of Yb atoms in a solid Ne matrix at a resolution of 0.025 nm. Five absorption bands were identified as due to transitions from the 4f145d06s21S04{f}^{14}5{d}^{0}6{s}^{2}{\phantom{\rule{4pt}{0ex}}}^{1}{S}_{0}4f145d06s21S0​ ground-state configuration to 4f145d06s6p4{f}^{14}5{d}^{0}6s6p4f145d06s6p and 4f135d16s24{f}^{13}5{d}^{1}6{s}^{2}4f135d16s2 configurations. The two lowest-energy bands were assigned to outer-shell transitions to 6s6p3P16s6p{\phantom{\rule{4pt}{0ex}}}^{3}{P}_{1}6s6p3P1​ and 1P1{}^{1}{P}_{1}1P1​ atomic states and displayed the structure of a broad doublet and an asymmetric triplet, respectively. The remaining three higher-frequency bands were assigned to inner-shell transitions to distinct J=1J=1J=1 states arising from the 4f135d16s24{f}^{13}5{d}^{1}6{s}^{2}4f135d16s2 configuration and were highly structured with narrow linewidths. A classical simulation was performed to identify the stability and symmetry of possible trapping sites in the Ne crystal. It showed that the overarching 1+21+21+2 structure of the high-frequency bands could be predominantly ascribed to crystal-field splitting in the axial field of a 10-atom vacancy of C4v{C}_{4v}C4v​ symmetry. Their prominent substructures were shown to be manifestations of phonon sidebands associated with the zero-phonon lines on each crystal-field state. Unprecedented for a metal--rare-gas system, resolution of individual phonon states on an allowed electronic transition was possible under excitation spectroscopy which reflects the semiquantum nature of solid Ne. In contrast to the absorption spectra, emission spectra produced by steady-state excitation into the 1P1{}^{1}{P}_{1}1P1​ absorption band consisted of simple, unstructured fluorescence bands.