Achieving high-resolution photoelectron spectroscopy from a broadband femtosecond laser pulse

Abstract

Femtosecond-induced resonance-enhanced multiphoton-ionization photoelectron spectroscopy (REMPI-PS) suffers from poor spectral resolution due to the large laser spectral bandwidth. In this paper, we present a scheme to achieve high-resolution REMPI-PS in the potassium atom by shaping the ultrashort femtosecond laser pulse. Our results show that the REMPI-PS bandwidth can be narrowed by several tens of times with a cubic spectral phase modulation, and thus high-resolution REMPI-PS and the fine structure of the energy-level diagram for multiple excited states can be obtained in spite of the broadband femtosecond laser pulse. Furthermore, we explain the physical control mechanism of the narrowband REMPI-PS by considering the two-photon power spectrum.

Quantum control of femtosecond resonance-enhanced multiphoton-ionization photoelectron spectroscopy

“…We theoretically propose a π or cubic phase modulation to realize the enhancement and narrowing of REMPI-PS [26][27][28][29]. In theory, the photoelectron spectral modulation was explained by the selective population of dressed states [21][22][23][24], or multiphoton power spectrum [28,29].…”

“…Recently, the advent of the femtosecond pulse shaping technique by modulating the laser spectral phase and/or amplitude in the frequency domain opened an opportunity to effectively control the femtosecond REMPI-PS. Various phase modulation schemes have been proposed to enhance or narrow the REMPI-PS [21][22][23][24][25][26][27][28][29], and some schemes have been experimentally realized [21][22][23][24][25]. For example, Wollenhaupt et al experimentally demonstrated the selective excitation of the slow and fast photoelectron components of REMPI-PS by sinusoidal, chirped, or phase-step modulation [21-24].…”

“…We theoretically propose a π or cubic phase modulation to realize the enhancement and narrowing of REMPI-PS [26][27][28][29]. In theory, the photoelectron spectral modulation was explained by the selective population of dressed states [21][22][23][24], or multiphoton power spectrum [28,29].In our previous works [26][27][28][29], the REMPI-PS was calculated by considering the laser field in time domain; thus the physical control mechanism of the photoelectron spectral modulation cannot be directly explained from this theoretical model, which greatly limits the understanding of the resonance-enhanced multiphoton-ionization process. However, in this paper we develop a theoretical model by considering the laser field in frequency domain and show that the REMPI process involves the on-and near-resonant excitation pathways, and therefore the photoelectron spectral modulation can be well explained by the inter-and intragroup interference involving these on-and near-resonant excitation pathways.…”

Resonance-enhanced multiphoton-ionization photoelectron spectroscopy by a rectangular amplitude modulation

“…The femtosecond laser pulse is an excellent tool to create the REMPI photoelectron spectroscopy because of its broad laser spectrum and high pulse intensity, while a main drawback for the femtosecondinduced REMPI photoelectron spectroscopy is low spectral resolution due to the broadband photoelectron spectrum. Recently, various methods by the femtosecond pulse shaping technique were proposed to narrow the REMPI photoelectron spectrum [19][20][21][22][23][24][25][26][27]. For example, Wollenhaupt et al showed that the REMPI photoelectron spectrum in potassium (K) atom can be narrowed by the selective excitation of the slow and fast photoelectrons using a sinusoidal, chirped, or * sazhang@phy.ecnu.edu.cn † zrsun@phy.ecnu.edu.cn phase-step modulation [19][20][21][22][23].…”

“…For example, Wollenhaupt et al showed that the REMPI photoelectron spectrum in potassium (K) atom can be narrowed by the selective excitation of the slow and fast photoelectrons using a sinusoidal, chirped, or * sazhang@phy.ecnu.edu.cn † zrsun@phy.ecnu.edu.cn phase-step modulation [19][20][21][22][23]. We showed that the REMPI photoelectron spectrum in cesium (Cs), sodium (Na), and K atoms can be tremendously narrowed by a cubic or π phase modulation [24][25][26][27]. These previous works aim to improve the spectral resolution by narrowing the photoelectron spectrum by the spectral phase modulation.…”