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TABLE I. The a-decay properties of the francium isotopes and their corresponding child and grandchild isotopes observed in the present work. The literature values are taken from Refs. [6,10]. The w decay reduced widths 5? and half-lives normalized to 7!*Po, calculated according to Ref. [26], are also given. In column 8, the spin and parity of the decaying state are given.

Table 1 I. The a-decay properties of the francium isotopes and their corresponding child and grandchild isotopes observed in the present work. The literature values are taken from Refs. [6,10]. The w decay reduced widths 5? and half-lives normalized to 7!*Po, calculated according to Ref. [26], are also given. In column 8, the spin and parity of the decaying state are given.

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FIG. 1. Schematic view of the focal-plane setup. In the present experiment only one large Ge-clover at the top position was used. The gas-filled recoil separator RITU [14] was used to separate evaporation residues formed in fusion evaporation reactions from the primary beam and to transport them to the focal plane. In the experiment the GREAT spectrometer [15] was used at the focal plane of RITU (Fig. 1). The GREAT setup consists of one multiwire proportional gas counter (MWPC) and two double-sided silicon strip detectors (DSSD). The silicon strip detectors have 60 vertical and 40 horizontal 1 mm
FIG. 1. Schematic view of the focal-plane setup. In the present experiment only one large Ge-clover at the top position was used. The gas-filled recoil separator RITU [14] was used to separate evaporation residues formed in fusion evaporation reactions from the primary beam and to transport them to the focal plane. In the experiment the GREAT spectrometer [15] was used at the focal plane of RITU (Fig. 1). The GREAT setup consists of one multiwire proportional gas counter (MWPC) and two double-sided silicon strip detectors (DSSD). The silicon strip detectors have 60 vertical and 40 horizontal 1 mm
FIG. 2. Energy spectra of w particles measured in the silicon detector and vetoed with the gas counter using the Ni + '4!Pr reaction: (a) all decays; (b) decays following recoil implants within 1 s; (c) parent decays followed by a second decay within 30 s; (d) child decays following a parent decay.
FIG. 2. Energy spectra of w particles measured in the silicon detector and vetoed with the gas counter using the Ni + '4!Pr reaction: (a) all decays; (b) decays following recoil implants within 1 s; (c) parent decays followed by a second decay within 30 s; (d) child decays following a parent decay.
FIG. 3. Parent and child a-particle energies for all chains of the type ER — a, — a,(—ag,.) observed in t Maximum search times were | s for t for the a, — a-(—a,-) pair. Dots are for he Ni + |4!Pr irradiation. he ER —a, pair and 60 s the a, — a, pairs and open diamonds represent the a, — a, pairs. Some of the identified groups are circled based on the two-sigma confid ence level obtained from the '8Rn distribution. Note: From figure it can be seen that in practice all the points are real correlations. The random correlations are expected ‘ to show up there where the strongest a ines’ are crossing. the an and w2n fusion-evaporation channels, respectively, can be identified. In the pn and p2n fusion-evaporation channels the radon isotopes '°?Rn and '°8Rn were produced. Finally the In, 2n, and 3n fusion evaporation channels yielded the francium isotopes 200Fy, 19°Fr and !°8Fr. For the francium isotopes triple a-decay chains, including the child activities
FIG. 3. Parent and child a-particle energies for all chains of the type ER — a, — a,(—ag,.) observed in t Maximum search times were | s for t for the a, — a-(—a,-) pair. Dots are for he Ni + |4!Pr irradiation. he ER —a, pair and 60 s the a, — a, pairs and open diamonds represent the a, — a, pairs. Some of the identified groups are circled based on the two-sigma confid ence level obtained from the '8Rn distribution. Note: From figure it can be seen that in practice all the points are real correlations. The random correlations are expected ‘ to show up there where the strongest a ines’ are crossing. the an and w2n fusion-evaporation channels, respectively, can be identified. In the pn and p2n fusion-evaporation channels the radon isotopes '°?Rn and '°8Rn were produced. Finally the In, 2n, and 3n fusion evaporation channels yielded the francium isotopes 200Fy, 19°Fr and !°8Fr. For the francium isotopes triple a-decay chains, including the child activities
FIG. 4. (Color online) Speculative w-decay schemes for !°Fr and !°8Fr are shown.
FIG. 4. (Color online) Speculative w-decay schemes for !°Fr and !°8Fr are shown.
TABLE II. Possible configurations and J” assignments. neighboring odd-mass polonium, astatine, radon and francium isotopes. The 13/2* isomeric state in odd-mass polonium and radon isotopes and the 1/2+ and the 13/2+ isomeric states in odd-mass astatine and francium isotopes are down sloping as a function of decreasing neutron number. At the same time the neutron state 5/2~ has an up sloping trend. In the case of 200Fr and |!°8At, some of the other multiplet members have energies between the 7+ and 3* states, with the result that the 7+ state is not w-particle decaying anymore. This assumption is supported by the in-beam measurement performed for !°8 At where almost all the y-ray transitions identified to feed the a-decaying 107 isomeric state were also seen in the a-particle decaying 3+ ground state tagged spectrum [30]. This supports the assumption that there is an F3 y-transition branch to the 7* state which is then followed by lower multipolarity y-ray transitions to the ground state. In the work [22] an isomeric state feeding the 3+ ground state in !°°At was reported. The y-ray transition was suggested to be a hindered E2 transition where the hindrance is due to structural changes. Since no sign of the 107 state has so far been reported for this nucleus (and neither for 7°°Fr) it is suggested that some other multiplet members come down between the 107 isomeric state and the 3* ground state allowing the y-ray transitions to overcome the a-particle decays. Finally the recent w-decay spectroscopy studies of '?* At and !**At support this picture [24,31]. In both cases two a-particle decaying isomeric states were identified. In '°*At the favoured w-particle decays do not feed the high and low spin states (10~- and 3*) states in '8*Bi directly but instead they feed excited states above these states. The a-particle decay from the high-spin state is followed by an M1 y-ray transition (165 keV) and the a-particle decay from the low spin state is followed by an E'1 (36 keV) transition. In 194 At the w-particle decay from the low-spin state is followed by a 76 keV (E1) y-ray transition. The high-spin states in 192 At and in !°4At were suggested to have the configuration 1 (2 f7/2)7/27 @v(i13/2)13/2*]9-, 10~. The configurations of the low-spin states were also discussed and it was suggested that they could originate from a configuration multiplet 7($1/2)1/2* @v(p3/2)3/27]1-, 2~. These assumptions are supported by the detailed spectroscopic measurements performed for the neighboring odd-mass astatine isotopes 191,193, 195 At [5, 6]. Since no clear sign of a-particle decays feeding the Leb 2... gg 8, JOA Ag 22.2. 84 gt dt. hw 2 ke gd
TABLE II. Possible configurations and J” assignments. neighboring odd-mass polonium, astatine, radon and francium isotopes. The 13/2* isomeric state in odd-mass polonium and radon isotopes and the 1/2+ and the 13/2+ isomeric states in odd-mass astatine and francium isotopes are down sloping as a function of decreasing neutron number. At the same time the neutron state 5/2~ has an up sloping trend. In the case of 200Fr and |!°8At, some of the other multiplet members have energies between the 7+ and 3* states, with the result that the 7+ state is not w-particle decaying anymore. This assumption is supported by the in-beam measurement performed for !°8 At where almost all the y-ray transitions identified to feed the a-decaying 107 isomeric state were also seen in the a-particle decaying 3+ ground state tagged spectrum [30]. This supports the assumption that there is an F3 y-transition branch to the 7* state which is then followed by lower multipolarity y-ray transitions to the ground state. In the work [22] an isomeric state feeding the 3+ ground state in !°°At was reported. The y-ray transition was suggested to be a hindered E2 transition where the hindrance is due to structural changes. Since no sign of the 107 state has so far been reported for this nucleus (and neither for 7°°Fr) it is suggested that some other multiplet members come down between the 107 isomeric state and the 3* ground state allowing the y-ray transitions to overcome the a-particle decays. Finally the recent w-decay spectroscopy studies of '?* At and !**At support this picture [24,31]. In both cases two a-particle decaying isomeric states were identified. In '°*At the favoured w-particle decays do not feed the high and low spin states (10~- and 3*) states in '8*Bi directly but instead they feed excited states above these states. The a-particle decay from the high-spin state is followed by an M1 y-ray transition (165 keV) and the a-particle decay from the low spin state is followed by an E'1 (36 keV) transition. In 194 At the w-particle decay from the low-spin state is followed by a 76 keV (E1) y-ray transition. The high-spin states in 192 At and in !°4At were suggested to have the configuration 1 (2 f7/2)7/27 @v(i13/2)13/2*]9-, 10~. The configurations of the low-spin states were also discussed and it was suggested that they could originate from a configuration multiplet 7($1/2)1/2* @v(p3/2)3/27]1-, 2~. These assumptions are supported by the detailed spectroscopic measurements performed for the neighboring odd-mass astatine isotopes 191,193, 195 At [5, 6]. Since no clear sign of a-particle decays feeding the Leb 2... gg 8, JOA Ag 22.2. 84 gt dt. hw 2 ke gd
FIG. 5. (Color online) Reduced-width 5? values are shown (a) for the even-mass astatine isotopes; (b) for the even-mass francium iso- topes. Tentative spin and parity assignments are given in brackets. A down-pointing arrow indicates that there is a competing £3 transition, but the £3 branch is unknown and a 100% a@ branch is assumed.
FIG. 5. (Color online) Reduced-width 5? values are shown (a) for the even-mass astatine isotopes; (b) for the even-mass francium iso- topes. Tentative spin and parity assignments are given in brackets. A down-pointing arrow indicates that there is a competing £3 transition, but the £3 branch is unknown and a 100% a@ branch is assumed.
FIG. 6. (Color online) Alpha-energy systematics are shown (a) for the even-mass astatine and francium isotopes; (b) for the odd-mass astatine and francium isotopes.
FIG. 6. (Color online) Alpha-energy systematics are shown (a) for the even-mass astatine and francium isotopes; (b) for the odd-mass astatine and francium isotopes.
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