Search

Purpose: The purpose of this study was to experimentally assess the possibility to monitor carbon ion range variations—due to tumor shift and/or elongation or shrinking—using prompt-gamma (PG) emission with inhomogeneous phantoms. Such a study is related to the development of PG monitoring techniques to be used in a carbon ion therapy context. Methods: A 95 MeV/u carbon ion beam was used to irradiate phantoms with a variable density along the ion path to mimic the presence of bone and lung in homogeneous humanlike tissue. PG profiles were obtained after a longitudinal scan of the phantoms. A setup comprising a narrow single-slit collimator and two detectors placed at 90° with respect to the beam axis was used. The time of flight technique was applied to allow the selection between PG and background events. Results: Using the positions at 50% entrance and 50% falloff of the PG profiles, a quantity called prompt-gamma profile length (PGPL) is defined. It is possible to observe shifts in the PGPL when there are absolute ion range shifts as small as 1–2 mm. Quantitatively, for an ion range shift of −1.33 ± 0.46 mm (insertion of a Teflon slab), a PGPL difference of −1.93 ± 0.58 mm and −1.84 ± 1.27 mm is obtained using a BaF2 and a NaI(Tl) detector, respectively. In turn, when an ion range shift of 4.59 ± 0.42 mm (insertion of a lung-equivalent material slab) is considered, the difference is of 4.10 ± 0.54 and 4.39 ± 0.80 mm for the same detectors. Conclusions: Herein, experimental evidence of the usefulness of employing PG to monitor carbon ion range using inhomogeneous phantoms is presented. Considering the homogeneous phantom as reference, the results show that the information provided by the PG emission allows for detecting ion range shifts as small as 1–2 mm. When considering the expected PG emission from an energy slice in a carbon ion therapy scenario, the experimental setup would allow to retrieve the same PGPL as the high statistics of the full experimental dataset in 58% of the times. However, this success rate increases to 93% when using a better optimized setup by means of Monte Carlo simulations.

A series of g-factor measurements in the Cl isotopes created as secondary radioactive beams at intermediate energies and employing the β-NMR technique have been recently carried out at GANIL. The results attempt to shed light on several open questions for the ground state properties of Cl isotopes, located just off the very interesting region of the island of inversion. Preliminary experimental results are presented and compared to shell-model calculations around N=28.

International audience; Prompt-gamma emission detection is a promising technique for hadrontherapy monitoring purposes. In this regard, obtaining prompt-gamma yields that can be used to develop monitoring systems based on this principle is of utmost importance since any camera design must cope with the available signal. Herein, a comprehensive study of the data from ten single-slit experiments is presented, five consisting in the irradiation of either PMMA or water targets with lower and higher energy carbon ions, and another five experiments using PMMA targets and proton beams. Analysis techniques such as background subtraction methods, geometrical normalization, and systematic uncertainty estimation were applied to the data in order to obtain absolute prompt-gamma yields in units of prompt-gamma counts per incident ion, unit of field of view, and unit of solid angle. At the entrance of a PMMA target, where the contribution of secondary nuclear reactions is negligible, prompt-gamma counts per incident ion, per millimetre and per steradian equal to (124 ± 0.7stat ± 30sys) × 10−6 for 95 MeV u−1 carbon ions, (79 ± 2stat ± 23sys) × 10−6 for 310 MeV u−1 carbon ions, and (16 ± 0.07stat ± 1sys) × 10−6 for 160 MeV protons were found for prompt gammas with energies higher than 1 MeV. This shows a factor 5 between the yields of two different ions species with the same range in water (160 MeV protons and 310 MeV u−1 carbon ions). The target composition was also found to influence the prompt-gamma yield since, for 300/310 MeV u−1 carbon ions, a 42% greater yield ((112 ± 1stat ± 22sys) × 10−6 counts ion−1 mm−1 sr−1) was obtained with a water target compared to a PMMA one.

The current diversity and inconsistency among published quadrupole moments calls for a thorough evaluation of the available data. In this work, a review of the ground-state Q-moments of the oxygen to calcium isotopes is presented, resulting in a revised database of 43 quadrupole moments. For every π (sd) isotope chain, the quadrupole moments are expressed relative to one reference isotope. This common reference rules out the existing arbitrariness and provides a reliable basis for future measurements and theoretical studies. In addition, the evaluated quadrupole-moment values are compared to shell-model calculations, obtained with different effective interactions in the sd and sdpf model spaces and using the standard effective charges e p = 1.3 e and e n = 0.5 e . The discrepancy between theory and experiment, observed for particular isotopes and isotope chains, calls for further fundamental research.

The electric quadrupole moment of the $_{13}^{33}\mathrm{Al}_{20}$ ground state, located at the border of the island of inversion, was obtained using continuous-beam $\ensuremath{\beta}$-detected nuclear quadrupole resonance ($\ensuremath{\beta}$-NQR). From the measured quadrupole coupling constant ${\ensuremath{\nu}}_{Q}=2.31(4)$ MHz in an $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ crystal, a precise value for the electric quadrupole moment is extracted: $\left|{Q}_{s}\left(^{33}\mathrm{Al}\right)\right|=141(3)$ mb. A comparison with large-scale shell model calculations shows that $^{33}\mathrm{Al}$ has at least 50% intruder configurations in the ground state wave function, favoring the excitation of two neutrons across the $N=20$ shell gap. $^{33}\mathrm{Al}$ therefore clearly marks the gradual transition north of the deformed Na and Mg nuclei towards the normal $Z\ensuremath{\ge}14$ isotopes.

Electric quadrupole moment Q of the Al 33 ground state has been measured by means of β-NMR spectroscopy using a spin-polarized Al 33 beam produced in a projectile fragmentation reaction. The obtained Q moment, | Q exp ( 33 Al ) | = 132 ( 16 ) e mb , shows a significant excess from the prediction of shell model calculations within the sd shell. The result indicates sizable admixing of pf intruder configurations in the ground state, demonstrating that the N = 20 shell closure certainly erodes in Al 33 , a nucleus located on the border of the island of inversion. Comparison was made with predictions of the Monte Carlo shell model, and also a particle-vibration coupling model treating the neutron pairing correlations in the ground state of Al 33 . Again, a significant admixture of pf intruder configurations to the Al 33 ground state was needed in both theoretical approaches to explain the observed large Q.

A new β -NMR / β -NQR setup is developed to study nuclear magnetic dipole moments and electric quadrupole moments at the LISE fragment separator at GANIL. Two key elements make the new design very powerful: the homogeneous magnet and the strong radio-frequency amplifier. The combination of both makes it possible to examine a broad spectrum of magnetic dipole and electric quadrupole moments. Several factors have an influence on the detection efficiency and on the sensitivity of the setup to observe a resonant change in the β -asymmetry : the thickness and the tilting angle of the implantation crystal, the material in the vacuum chamber, the applied magnetic field and the Q β -value of the decaying nuclei. A detailed study of these effects is made using a dedicated GEANT4 Monte Carlo simulation code.

The electric quadrupole coupling constant of the 31 Al ground state is measured to be ν Q = | e Q V z z h | = 2196 ( 21 ) kHz using two different β -NMR (Nuclear Magnetic Resonance) techniques. For the first time, a direct comparison is made between the continuous rf technique and the adiabatic fast passage method. The obtained coupling constants of both methods are in excellent agreement with each other and a precise value for the quadrupole moment of 31 Al has been deduced: | Q ( Al 31 ) | = 134.0 ( 16 ) mb . Comparison of this value with large-scale shell-model calculations in the sd and sdpf valence spaces suggests that the 31 Al ground state is dominated by normal sd-shell configurations with a possible small contribution of intruder states. The obtained value for | Q ( Al 31 ) | and a compilation of measured quadrupole moments of odd- Z even- N isotopes in comparison with shell-model calculations shows that the proton effective charge e p = 1.1 e provides a much better description of the nuclear properties in the sd-shell than the adopted value e p = 1.3 e .

For the first time the g factor of an isotope beyond N = 20 near the ‘island of inversion’ has been measured. A 34Al radioactive beam was produced in a one-neutron pickup reaction on a 36S primary beam at 77.5 MeV/u, providing a large spin-polarization for application of the β-Nuclear Magnetic Resonance (β-NMR) method. The measured g factor of 34Al, | g | = 0.539 ( 2 ) , combined with results from earlier β-decay studies, allows to firmly assign a ground state spin/parity 4 − . Comparison to large scale shell model calculations reveals that a dominant amount of intruder components is needed in the 34Al wave function to account for the observed large magnetic moment μ = ( + ) 2.156 ( 16 ) μ N . This reveals Z = 13 to be a true ‘transition number’ between the normal Z = 14 Si isotopes and the abnormal Z = 12 Mg isotopes. The sensitivity of this odd–odd ground state dipole moment to the N = 20 , as well as the N = 28 gap, reveals that both are significantly reduced, despite Z = 13 being outside the conventional island of inversion.

The purpose of this study was to experimentally assess the possibility to monitor carbon ion range variations--due to tumor shift and/or elongation or shrinking--using prompt-gamma (PG) emission with inhomogeneous phantoms. Such a study is related to the development of PG monitoring techniques to be used in a carbon ion therapy context.A 95 MeV/u carbon ion beam was used to irradiate phantoms with a variable density along the ion path to mimic the presence of bone and lung in homogeneous humanlike tissue. PG profiles were obtained after a longitudinal scan of the phantoms. A setup comprising a narrow single-slit collimator and two detectors placed at 90° with respect to the beam axis was used. The time of flight technique was applied to allow the selection between PG and background events.Using the positions at 50% entrance and 50% falloff of the PG profiles, a quantity called prompt-gamma profile length (PGPL) is defined. It is possible to observe shifts in the PGPL when there are absolute ion range shifts as small as 1-2 mm. Quantitatively, for an ion range shift of -1.33 ± 0.46 mm (insertion of a Teflon slab), a PGPL difference of -1.93 ± 0.58 mm and -1.84 ± 1.27 mm is obtained using a BaF2 and a NaI(Tl) detector, respectively. In turn, when an ion range shift of 4.59 ± 0.42 mm (insertion of a lung-equivalent material slab) is considered, the difference is of 4.10 ± 0.54 and 4.39 ± 0.80 mm for the same detectors.Herein, experimental evidence of the usefulness of employing PG to monitor carbon ion range using inhomogeneous phantoms is presented. Considering the homogeneous phantom as reference, the results show that the information provided by the PG emission allows for detecting ion range shifts as small as 1-2 mm. When considering the expected PG emission from an energy slice in a carbon ion therapy scenario, the experimental setup would allow to retrieve the same PGPL as the high statistics of the full experimental dataset in 58% of the times. However, this success rate increases to 93% when using a better optimized setup by means of Monte Carlo simulations.

A negative magnetic moment of 23Mg has been determined by collinear laser spectroscopy at CERN-ISOLDE. The absolute value is in agreement with previous measurements by nuclear magnetic resonance while the sign points at high-seniority configurations. The result is consistent with shell-model predictions for nuclei with valence nucleons in the sd shell. ispartof: Journal of Physics G, Nuclear and Particle Physics vol:44 issue:7 status: published

A marked difference in the nuclear charge radius was observed between the ${I}^{\ensuremath{\pi}}={3}^{+}$ ground state and the ${I}^{\ensuremath{\pi}}={0}^{+}$ isomer of $^{38}\mathrm{K}$ and is qualitatively explained using an intuitive picture of proton-neutron pairing. In a high-precision measurement of the isomer shift using bunched-beam collinear laser spectroscopy at CERN-ISOLDE, a change in the mean-square charge radius of $⟨{r}_{\mathrm{c}}^{2}⟩{(}^{38}{\mathrm{K}}^{m})\ensuremath{-}⟨{r}_{\mathrm{c}}^{2}⟩{(}^{38}{\mathrm{K}}^{g})=0.100(6)\text{ }\text{ }{\mathrm{fm}}^{2}$ was obtained. This is an order of magnitude more accurate than the result of a previous indirect measurement from which it was concluded that both long-lived states in $^{38}\mathrm{K}$ have similar charge radii. Our observation leads to a substantially different understanding since the difference in charge radius is, moreover, opposite in sign to previously reported theoretical predictions. It is demonstrated that the observed isomer shift can be reproduced by large-scale shell-model calculations including proton and neutron excitations across the $N,Z=20$ shell gaps, confirming the significance of cross-shell correlations in the region of $^{40}\mathrm{Ca}$.

A marked difference in the nuclear charge radius was observed between the I^{π}=3^{+} ground state and the I^{π}=0^{+} isomer of ^{38}K and is qualitatively explained using an intuitive picture of proton-neutron pairing. In a high-precision measurement of the isomer shift using bunched-beam collinear laser spectroscopy at CERN-ISOLDE, a change in the mean-square charge radius of ⟨r_{c}^{2}⟩(^{38}K^{m})-⟨r_{c}^{2}⟩(^{38}K^{g})=0.100(6) fm^{2} was obtained. This is an order of magnitude more accurate than the result of a previous indirect measurement from which it was concluded that both long-lived states in ^{38}K have similar charge radii. Our observation leads to a substantially different understanding since the difference in charge radius is, moreover, opposite in sign to previously reported theoretical predictions. It is demonstrated that the observed isomer shift can be reproduced by large-scale shell-model calculations including proton and neutron excitations across the N,Z=20 shell gaps, confirming the significance of cross-shell correlations in the region of ^{40}Ca.

\item[Background] Ground-state spins and magnetic moments are sensitive to the nuclear wave function, thus they are powerful probes to study the nuclear structure of isotopes far from stability. \item[Purpose] Extend our knowledge about the evolution of the $1/2^+$ and $3/2^+$ states for K isotopes beyond the $N = 28$ shell gap. \item[Method] High-resolution collinear laser spectroscopy on bunched atomic beams. \item[Results] From measured hyperfine structure spectra of K isotopes, nuclear spins and magnetic moments of the ground states were obtained for isotopes from $N = 19$ up to $N = 32$. In order to draw conclusions about the composition of the wave functions and the occupation of the levels, the experimental data were compared to shell-model calculations using SDPF-NR and SDPF-U effective interactions. In addition, a detailed discussion about the evolution of the gap between proton $1d_{3/2}$ and $2s_{1/2}$ in the shell model and {\it{ab initio}} framework is also presented. \item[Conclusions] The dominant component of the wave function for the odd-$A$ isotopes up to $^{45}$K is a $\pi 1d_{3/2}^{-1}$ hole. For $^{47,49}$K, the main component originates from a $\pi 2s_{1/2}^{-1}$ hole configuration and it inverts back to the $\pi 1d_{3/2}^{-1}$ in $^{51}$K. For all even-$A$ isotopes, the dominant configuration arises from a $\pi 1d_{3/2}^{-1}$ hole coupled to a neutron in the $\nu 1f_{7/2}$ or $\nu 2p_{3/2}$ orbitals. Only for $^{48}$K, a significant amount of mixing with $\pi 2s_{1/2}^{-1} \otimes \nu (pf)$ is observed leading to a $I^{\pi}=1^{-}$ ground state. For $^{50}$K, the ground-state spin-parity is $0^-$ with leading configuration $\pi 1d_{3/2}^{-1} \otimes \nu 2p_{3/2}^{-1}$., Comment: 12 pages, 10 figures, 7 tables

International audience; Prompt secondary radiations such as gamma rays and protons can be used for ion-range monitoring during ion therapy either on an energy-slice basis or on a pencil-beam basis. We present a review of the ongoing activities in terms of detector developments, imaging, experimental and theoretical physics issues concerning the correlation between the physical dose and hadronic processes

The ground-state spins and magnetic moments of $^{49,51}\mathrm{K}$ have been measured using bunched-beam high-resolution collinear laser spectroscopy at ISOLDE CERN. For $^{49}\mathrm{K}$ a ground-state spin $I=1/2$ was firmly established. The observed hyperfine structure of $^{51}\mathrm{K}$ requires a spin $Ig1/2$ and strongly suggests $I=3/2$. From its magnetic moment $\ensuremath{\mu}(^{51}\mathrm{K})=+0.5129(22){\ensuremath{\mu}}_{N}$ a spin-parity ${I}^{\ensuremath{\pi}}=3/{2}^{+}$ with a dominant $\ensuremath{\pi}1{d}_{3/2}^{\ensuremath{-}1}$ hole configuration was deduced. This establishes for the first time the reinversion of the single-particle levels and illustrates the prominent role of the residual monopole interaction for single-particle levels and shell evolution.

Charge radii of all magnesium isotopes in the sd shell have been measured, revealing evolution of the nuclear shape throughout two prominent regions of assumed deformation centered on (24)Mg and (32)Mg. A striking correspondence is found between the nuclear charge radius and the neutron shell structure. The importance of cluster configurations towards N=8 and collectivity near N=20 is discussed in the framework of the fermionic molecular dynamics model. These essential results have been made possible by the first application of laser-induced nuclear orientation for isotope shift measurements.

Charge radii of all magnesium isotopes in the sd shell have been measured, revealing evolution of the nuclear shape throughout two prominent regions of assumed deformation centered on (24)Mg and (32)Mg. A striking correspondence is found between the nuclear charge radius and the neutron shell structure. The importance of cluster configurations towards N=8 and collectivity near N=20 is discussed in the framework of the fermionic molecular dynamics model. These essential results have been made possible by the first application of laser-induced nuclear orientation for isotope shift measurements.

Measurements of the ground-state nuclear spins and magnetic and quadrupole moments of the copper isotopes from $^{61}\mathrm{Cu}$ up to $^{75}\mathrm{Cu}$ are reported. The experiments were performed at the CERN online isotope mass separator (ISOLDE) facility, using the technique of collinear laser spectroscopy. The trend in the magnetic moments between the $N=28$ and $N=50$ shell closures is reasonably reproduced by large-scale shell-model calculations starting from a $^{56}\mathrm{Ni}$ core. The quadrupole moments reveal a strong polarization of the underlying Ni core when the neutron shell is opened, which is, however, strongly reduced at $N=40$ due to the parity change between the $\mathit{pf}$ and $g$ orbits. No enhanced core polarization is seen beyond $N=40$. Deviations between measured and calculated moments are attributed to the softness of the $^{56}\mathrm{Ni}$ core and weakening of the $Z=28$ and $N=28$ shell gaps.

This article reports on the ground-state spin and moments measured in $^{72,74}\mathrm{Cu}$ using collinear laser spectroscopy at the CERN On-Line Isotope Mass Separator (ISOLDE) facility. From the measured hyperfine coefficients, the nuclear observables $\ensuremath{\mu}$(${}^{72}\mathrm{Cu})=\ensuremath{-}1.3472(10){\ensuremath{\mu}}_{N}$, $\ensuremath{\mu}({}^{74}\mathrm{Cu})=\ensuremath{-}1.068(3){\ensuremath{\mu}}_{N}$, $Q({}^{72}\mathrm{Cu})=+8(2) {\mathrm{efm}}^{2}$, $Q({}^{74}\mathrm{Cu})=+26(3) {\mathrm{efm}}^{2}$, $I({}^{72}\mathrm{Cu})=2$, and $I({}^{74}\mathrm{Cu})=2$ have been determined. Through a comparison of the measured magnetic moments with different models, the negative moment reveals a strong $\ensuremath{\pi}{f}_{5/2}\ensuremath{\bigotimes}\ensuremath{\nu}{g}_{9/2}$ component in the ground-state wave function. Consequently, a negative parity has been assigned to the ground states of $^{72,74}\mathrm{Cu}$. Large-scale shell-model calculations illustrate the strong sensitivity of the nuclear moments to configuration mixing and to the effective interaction employed.

A Comment on the Letter by Vandana Tripathi et al., Phys. Rev. Lett. 101, 142504 (2008). The authors of the Letter offer a Reply.

The $g$ factor of the $^{44}\mathrm{Cl}$ ground state is measured at the LISE fragment separator at the Grand Acc\'el\'erateur National d'Ions Lourds (GANIL) using the $\ensuremath{\beta}$ nuclear magnetic resonance technique, resulting in $g$($^{44}\mathrm{Cl}$)$=(\ensuremath{-})0.2749(2)$. An analysis of the $g$ factor value and of the theoretical level scheme in the shell-model framework reveals the presence of odd-proton ${s}_{1/2}$ configurations and neutron excitation across the $N=28$ shell gap in the ground state of $^{44}\mathrm{Cl}$. In addition, the measured $g$ factor strongly supports a ${2}^{\ensuremath{-}}$ spin assignment for the $^{44}\mathrm{Cl}$ ground state.

The nuclear electric quadrupole moment (Q moment) of the neutron-rich nucleus 33Al (I = 5/2 , T 1/2 = 41 ms) has been measured by the $ \beta$ -ray detected nuclear quadrupole resonance ( $ \beta$ -NQR) method for the first time. The 33Al nucleus is considered to be on the border of the island of inversion within which a significant intrusion of the pf orbits occurs across the N = 20 shell gap and the intrusion causes an anomalous enhancement of the Q moment. Polarized 33Al nuclei were produced from 36S (77.5MeV/u beams through the fragmentation process and separated by LISE fragment separator at GANIL. The 33Al nuclei were implanted into a Al2O3 single-crystal plate and the $ \beta$ -NQR spectrum was successfully obtained.

We report the first confirmation of the predicted inversion between the pi2p3/2 and pi1f5/2 nuclear states in the nu(g)9/2 midshell. This was achieved at the ISOLDE facility, by using a combination of in-source laser spectroscopy and collinear laser spectroscopy on the ground states of 71,73,75Cu, which measured the nuclear spin and magnetic moments. The obtained values are mu(71Cu)=+2.2747(8)mu(N), mu(73Cu)=+1.7426(8)mu(N), and mu(75Cu)=+1.0062(13)mu(N) corresponding to spins I=3/2 for 71,73Cu and I=5/2 for 75Cu. The results are in fair agreement with large-scale shell-model calculations.

The g factors of the {sup 17}N and {sup 18}N ground states were remeasured using the {beta}-nuclear magnetic resonance ({beta}-NMR) technique on spin-polarized fragment beams at the LISE fragment separator at GANIL. Based on the g-factor results, the magnetic moments of {sup 17}N (I{sup {pi}}=1/2{sup -}) and {sup 18}N (I{sup {pi}}=1{sup -}) were deduced: |{mu}({sup 17}N)|=0.3551(4) {mu}{sub N} and |{mu}({sup 18}N)|=0.3273(4) {mu}{sub N}. Both results are in good agreement with and more precise than the earlier observed values.

New sub-mu s isomers have been observed in the neutron-rich Sn isotopes. Sn-125,Sn-127,Sn-129 nuclei have been produced in a relativistic fission reaction of U-238 on a Be-9 target at 750 A.MeV and by the fragmentation of Xe-136 at 600 A.MeV populating high-spin yrast states. In addition to the already known mu s isomers, three new ones with sub-mu s half-lives have been observed. These yrast isomers are the high-spin members of the nu(d(3/2)(-1)h(11/2)(-2)) and nu h(11/2)(-n), seniority v = 3 multiplets leading to isomeric (23/2(+)) and (27/2(-)) states, respectively. Added to the already known 19/2(+)mu s isomers in this region the current work completes the systematic information of neutron-hole excitations toward the filling of the last h(11/2) orbital at N = 82. The results are discussed in the framework of state-of-the-art shell-model calculations using realistic interactions.

We report on the first determination of the nuclear ground-state spin of $^{33}\mathrm{Mg}$, $I=3/2$, and its magnetic moment, $\ensuremath{\mu}=\ensuremath{-}0.7456(5)\text{ }{\ensuremath{\mu}}_{N}$, by combining laser spectroscopy with nuclear magnetic resonance techniques. These values are inconsistent with an earlier suggested 1 particle-1 hole configuration and provide evidence for a 2 particle-2 hole intruder ground state with negative parity. The results are in agreement with an odd-neutron occupation of the $3/2\text{ }[321]$ Nilsson orbital at a large prolate deformation. The discussion emphasizes the need of further theoretical and experimental investigation of the island of inversion, a region previously thought to be well understood.

We report on the first determination of the nuclear ground-state spin of 33Mg, I=3/2, and its magnetic moment, mu= -0.7456(5) mu(N), by combining laser spectroscopy with nuclear magnetic resonance techniques. These values are inconsistent with an earlier suggested 1 particle-1 hole configuration and provide evidence for a 2 particle-2 hole intruder ground state with negative parity. The results are in agreement with an odd-neutron occupation of the 3/2 [321] Nilsson orbital at a large prolate deformation. The discussion emphasizes the need of further theoretical and experimental investigation of the island of inversion, a region previously thought to be well understood.

The quadrupole moment of the 8{sup +} yrast state in {sup 84}Kr was measured using the level-mixing spectroscopy technique to be Q= 36(4) e fm{sup 2}. The result is compared with predictions of the shell model using common sets of effective charges. The comparison of experimental quadrupole moments with calculated values for 8{sup +} states in Kr, Sr and Zr isotopes with N= 48, 50 and for 9/2{sup +} states in isotopes with N= 47, 49 suggests a modification of the effective charges used in this region.