(The) Studies of molecular structures of alkali metal dimers by high resolution molecular spectroscopy in a supersonic molecular beam

Abstract

High resolution resonance enhanced two photon ionization spectroscopy of RbCs near 520 nm: The $5^1Σ^{+}$ state. The first rotationally resolved high resolution excitation spectrum of RbCs is obtained near 520 nm by resonance enhanced two photon ionization (RE2PI) study. The excited electronic state is assigned to the $5^1Σ^{+}$ state by the spectrum analysis and comparison with ab initio calculations. The spectroscopic constants of the $5^1Σ^{+}$ state are determined to be $T_e=18564.560(76)cm^{-1}$, $ω_e=39.193(25)cm^{-1}$, $R_e=4.951(5)Å$. The Rydberg-Klein-Rees (RKR) potential curve is constructed and compared with theoretical calculations. Avoided crossings between the $5^1Σ^{+}$ and $6^1Σ^{+}$ states of RbCs are observed. Very complex resonance enhanced two photon ionization spectrum of RbCs near 640 nm: The $2 ^3π_0$ state and the strongly perturbed $2 ^1π_1$, $2 ^3π_1$, and $3 ^3Σ^{+}_1$ states. Very complicated resonance enhanced two-photon ionization (RE2PI) spectrum of RbCs is observed near 640 nm by combining the molecular beam and time-of-flight mass spectrometer. In this region, the potential curves of the $2^1π$, $2^3π$, and $3^3Σ^{+}$ states cross with one another. The $2^1π_1$, $2^3π_0$, $2^3π_1$, and $3^3Σ^{+}_1$ states can be directly observed by the single photon transition from the X $^1Σ^{+}$ state. Just one vibrational progression is assigned in this complex spectrum, and the excited state of this progression is assigned to the $2^3π_0$ state by the comparison with experimentally obtained and ab initio calculated values. The molecular constants of the $2^3π_0$ state are determined to be $T_e=15348.28(1) cm^{-1}$, $ω_e=30.52(2) cm^{-1}$, and $R_e=4.95(4)Å$. From the high resolution analysis, the other transitions except the $2^3π_0$- X $^1Σ^{+}$ transition correspond to the perpendicular transitions with P, Q, and R branches. The excited states of these perpendicular transitions could not be exactly assigned. The spin-orbit perturbation a...