Ⅰ. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 50 (2017)

Gas-phase chemistry of Re carbonyl complexes with short-lived isotopes
Y. Wang,䠆1 Z. Qin,䠆1 F. Fan,䠆1 H. Haba,䠆2 Y. Komori,䠆2 S. Yano,䠆2 D. Kaji,䠆2 K. Morimoto,䠆2 and S. Cao䠆1Since the first organometallic compound of asuperheavy element, Sg(CO)6, was successfully synthesized
in 2014,1) the door was opened for nuclear chemists tofurther study the carbonyl complexes of heavier elements
such as bohrium hassium, and even meitnerium. The nextachievement was suggested to be the chemical investigationof mononuclear Bh carbonyl complexes Bh(CO)5. First,
however, the chemical properties of its lighter homologs
Tc(CO)5 and Re(CO)5 required study. We previously
investigated the chemical behaviours of Tc(CO)5,2) Ru(CO)5,
and Rh(CO)4.3) In this study, we performed a gas-phasechemical experiment on Re carbonyls with short-lived
isotopes. The volatile Re carbonyls were synthesized andtheir adsorption enthalpies on a perfluorinatedethylene-propylene (FEP) Teflon surface were determinedusing low temperature isothermal chromatography (IC).
Furthermore, the relative chemical yields of these Re
carbonyls were obtained for the first time, which is very
important for the future chemical investigation of Bh
carbonyl complexes.
A natGd2O3 target with a thickness of 340 ȝg/cm2 wasprepared by electrodeposition onto a 2-ȝm Ti foil. The23
Na7+ ion beam was extracted from RILAC. The beamenergy was 130.6 MeV at the middle of the target, and thetypical beam intensity was 2.5 particle ȝA. The short-lived
Re isotopes were produced in the heavy-ion reactions
natGd(23Na,xn)172-177Re.4) GARIS was employed topreseparate the evaporation residues (ERs). For GARIS, themagnetic rigidity was 1.74 Tm and the He pressure was 33
Pa. The ERs were then guided into a recoil transfer chamber(RTC) with an inert internal surface through a 0.7-ȝm
Mylar window that was supported by a honeycomb-holegrid with 84% transparency. In RTC, the ERs werethermalized in the mixed gas containing CO (high-purity
CO/ He or high-purity CO/Ar), formed volatile carbonyl
complexes in situ, and then were transported through a 10m long Teflon (FEP) capillary (i.d.= 2 mm) to an IC device.
The ERs could also be transported with KCl aerosols by aHe gas-jet to the chemistry laboratory to evaluate relative
chemical yields. The total gas flow rate was maintained at 1
L/min, and the pressure in the RTC chamber was around 80kPa. The depths of the RTC were 7 and 100 mm for the Ar
and He gas, respectively.
The gas-phase chemical behaviors of Re carbonyl
complexes were systematically studied using an online lowtemperature IC with the Ar and CO mixture. A 5.28-m long
IC column made of Teflon (i.d.= 2 mm) was used to obtainthe chemical information of the high-volatile Re carbonyls.
After passing through the IC column, the surviving
volatile carbonyls were collected with 800 mg of activated䠆1
䠆2

charcoal powders in a glass tube (4-mm i.d. × 5 cm length)
facing a high-purity Ge-Ȗ-ray detector with a relative
efficiency of 20% (EG&G Ortec). By fitting thebreakthrough curves of the corresponding carbonyl
complexes using a Monte Carlo simulation program,2) it
was found that three short-lived 172m,174,176Re isotopes yield
the same adsorption enthalpy on the Teflon surface ǻHads =kJ mol-1, which is consistent with the literature.5)
43+2-1
Figure 1 shows the chemical yields of 172mRe, 174Re,176
and Re carbonyls as a function of the CO concentrationin the He gas relative to the yields obtained with the KClaerosols in the He gas. The CO concentration was varied
from 0% to 100% and all the data were normalized by theirradiation dose. The highest relative chemical yields for174
Re and 176Re carbonyls appeared at a 50% CO
concentration with a value of around 25%. This value is thesame as its lighter homolog Tc carbonyl (about 25%).2)
However, for the 172mRe carbonyl complex, the highest
relative chemical yield decreased to 10%, because of theshorter half-life and long transport time from the RTC to thecharcoal trap. This study could help us to optimize theexperimental conditions for future chemical behavior studyof the Bh carbonyl complexes.

Fig. 1. Chemical yields of 172m,174,176Re carbonyls
transported with a CO and He mixed gas. The 100% value
is the yield obtained with KCl aerosols in the He carrier gas.
References
1) J. Even et al., Science 345, 1491 (2014).
2) Y. Wang et al., Phys. Chem. Chem. Phys. 17, 13228 (2015).
3) S. Cao et al., Phys. Chem. Chem. Phys. 18, 119 (2016).
4) H. Haba et al., RIKEN Accel. Prog. Rep. 45, 293 (2015).
5) J. Even et al., Radiochim. Acta 102 (12), 1093 (2014).

Institute of Modern Physics, Chinese Academy of Sciences
RIKEN Nishina Center- 25 -