�N���X�^�[�C�I���E���q�Փˑ��u��p���AH⁺(H₂O)_n(n=2-9)��D₂O�Ƃ̏Փˎ������s�Ȃ����B���̌���H/D�������ϑ����ꂽ�B�������ʂ���N���X�^�[�T�C�Y����H/D�������x�萔�����߂��BH/D�������x�萔�̓N���X�^�[�T�C�Y�ˑ����������A�T�C�Y���������قǑ傫���l���������Ƃ��킩�����B�����ŁA���̈ˑ����̗��R�ɂ‚��Č�������B

The H/D exchange was observed in the collision of H⁺(H₂O)_n(n=2-9) with D₂O at low translational energies. We evaluated H/D exchange rate constants using the data obtained experimentally. It was found that the H/D exchange rate constants were strongly dependent on the cluster size and possessed larger values as the cluster size decreased. We discuss the reason for this size dependence.