We present SpectrumSDT – a program for calculations of energies and lifetimes of bound rotational-vibrational states below and scattering resonances above the dissociation threshold on a global potential energy surface of a triatomic system, which may include stable molecules, weekly-bound van-der-Waals complexes, and unbound atom + diatom scattering systems. Large-amplitude vibrational motion is treated explicitly using hyper-spherical coordinates. Three options for the rotational-vibrational interaction are supported: uncoupled (symmetric top rotor), partially coupled (to include interaction between several nearest states only) and full-coupled (vibrating asymmetric-top rotor). In addition to energies and lifetimes, SpectrumSDT is able to integrate ro-vibrational wave functions over the user-defined regions of potential energy surface, which helps to classify these states. In this release of the code, SpectrumSDT is limited to ABA-type molecules with wave functions that do not extend into the regions near Eckart singularities.

Program summary

Program title: SpectrumSDT

CPC Library link to program files: https://doi.org/10.17632/9gftxjs4yk.1

Developer's repository link: https://github.com/IgorGayday/SpectrumSDT

Licensing provisions: GNU General Public License 3 (GPL)

Programming language: Fortran

Nature of problem: Calculations of energies and lifetimes of bound rotational-vibrational states below and scattering resonances above the dissociation threshold on a global potential energy surface of a triatomic system, which may include stable molecules, weekly-bound van-der-Waals complexes, and unbound atom + diatom scattering systems.

Solution method: A Hamiltonian matrix is built in APH coordinates using an optimal 2D basis set, adjusted for a given problem. A complex absorbing potential (CAP) is added to define a boundary condition for calculation of scattering resonances above the dissociation threshold. The eigenstates of the Hamiltonain matrix are found using a state-of-the-art iterative eigensolver.

Restrictions: The present version is restricted to ABA-molecules and wave functions that do not extend into linear and equilateral triangle configurations.

Additional comments including restriction and unusual features: Probabilities and lifetimes of the wave functions can be calculated in user-defined regions on the PES, which allows to analyze their localization properties (i.e. automatic isotopomer assignment) and obtain channel-specific lifetimes for scattering resonances.

中文翻译：

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SpectrumSDT：用于并行计算三原子系统中结合状态和散射共振的旋转振动能量和寿命的程序

我们展示了 SpectrumSDT——一个用于计算能量和寿命的程序，用于计算以下束缚旋转振动状态和散射共振高于三原子系统全局势能表面的解离阈值，其中可能包括稳定分子、每周结合的范德华复合物和未结合的原子 + 硅藻散射系统。使用超球面坐标明确处理大振幅振动运动。支持旋转振动相互作用的三个选项：非耦合（对称顶部转子）、部分耦合（仅包括几个最近状态之间的相互作用）和完全耦合（振动非对称顶部转子）。除了能量和寿命之外，SpectrumSDT 还能够在用户定义的势能表面区域上集成旋转振动波函数，这有助于对这些状态进行分类。在此版本的代码中，奇点。

程序概要

节目名称： SpectrumSDT

CPC 库程序文件链接： https : //doi.org/10.17632/9gftxjs4y​​k.1

开发者仓库链接： https : //github.com/IgorGayday/SpectrumSDT

许可条款：GNU 通用公共许可证 3 (GPL)

编程语言：Fortran

问题的性质：计算三原子系统的全局势能表面上低于解离阈值的结合旋转振动状态的能量和寿命和高于解离阈值的散射共振，其中可能包括稳定分子、每周结合的范德瓦尔斯复合物、和未结合的原子 + 硅藻散射系统。

求解方法：哈密​​顿矩阵是在 APH 坐标中使用最优 2D 基组构建的，并针对给定问题进行了调整。添加复合吸收势 (CAP) 以定义边界条件，用于计算离解阈值以上的散射共振。Hamiltonain 矩阵的特征态是使用最先进的迭代特征求解器找到的。

限制：当前版本仅限于不扩展为线性和等边三角形配置的 ABA 分子和波函数。

附加说明，包括限制和不寻常的特征：波函数的概率和寿命可以在 PES 上的用户定义区域中计算，这允许分析它们的定位特性（即自动同位素异构体分配）并获得散射共振的特定通道寿命。