Attosecond transient absorption spectroscopy of molecular nitrogen: Vibrational coherences in the b′ 1Σ+u state

Abstract

Nuclear and electronic dynamics in a wavepacket comprising bound Rydberg and valence electronic states of nitrogen from 12 to 15 eV are investigated using attosecond transient absorption. Vibrational quantum beats with a fundamental period of 50 femtoseconds persist for a picosecond in the b 0 1 R + u valence state. Multi-state calculations show that these coherences result primarily from near infraredinduced coupling between the inner and outer regions of the b 0 1 R + u state potential and the dark a 00 1 R + g state. The excellent spectral and temporal resolution of this technique allows measurement of the anharmonicity of the b 0 1 R + u potential directly from the observed quantum beats.

Attosecond transient-absorption spectroscopy of polar molecules

“…Given the weak intensity of the UV field, we can treat its interaction with the system perturbatively. To zeroth order in the UV field the coefficients remain unchanged, and we have a (19) where W N (t − τ ) is the window function described in the text at the start of Sec. III, which reproduces the abrupt suppression of the dipole moment due to dissociating wave packets in models with free nuclei.…”

“…Equations (19), (20), and (23) give rise to the LISs, and from them we can surmise the origins and properties of the LISs. Evidently, both the off-diagonal (D 12 ) and diagonal (D 11 , D 22 ) dipole matrix elements are essential.…”

Multidimensional spectroscopy with attosecond extreme ultraviolet and shaped near-infrared pulses

“…High harmonic generation (HHG)–based experiments are capable of routinely producing isolated pulses that support durations <100 as ( 6 ) with sufficient timing stability and flux to efficiently probe these processes ( 7 ). The large bandwidth associated with these pulses creates complex coherent superpositions of states (wave packets) spanning multiple electronic and vibrational levels ( 8 ). Typical attosecond spectroscopy experiments use isolated attosecond pulses in combination with intense broadband near-infrared (NIR) pulses to preserve the time resolution provided by the attosecond pulse while compensating for its weak intensity.…”

“…Typical attosecond spectroscopy experiments use isolated attosecond pulses in combination with intense broadband near-infrared (NIR) pulses to preserve the time resolution provided by the attosecond pulse while compensating for its weak intensity. Attosecond transient absorption in which an XUV pulse is followed by a NIR pulse has been an especially powerful tool to study dynamics of excited states located in the XUV in both atomic and molecular systems ( 3 , 8 , 9 ). However, the temporal dependence observed in these experiments is complex because many couplings between excited states induced by the NIR pulses are spatially overlapped.…”

Analytic modeling of structures in attosecond transient-absorption spectra

“…ATAS has enabled the exploration of various processes on their natural time scales, as exemplified by numerous investigations; for instance, in the observation of strong field dynamics and ionization in several systems [4][5][6][7], autoionization in Ar [8], and the control of wave packets in He [9]. The method has also been successfully applied to molecular systems, such as in experimental studies on N 2 [10,11] and in theoretical studies on charge migration [12] and the effects of nuclear dynamics [13].…”