## 1 Introduction  
Multiwavelength ultrafast radiation sources in the \(\sim\)1-1.3 \(\upmu\)m wavelength range are of great importance for the two-photon imaging of living tissues [1]. It has recently been shown that a \(-\)50-100% greater imaging depth can be obtained using excitation at wavelengths of \(-\)1050-1700 nm compared to 800 nm [2, 3]. Increasing the wavelength of driving femtosecond laser pulses by nonlinear conversion makes it possible to generate attosecond X-ray pulses with higher photon energy [4] and improve the efficiency of THz generation [5]. In particular, the technology of intense THz radiation sources (with peak fields \(>\) 1 GV/cm\({}^{2}\)) is based on the optical rectification of femtosecond pulses in highly nonlinear organic crystals. The main challenge for such applications is the need for high-energy pump lasers at relatively difficult-to-reach wavelengths of \(\sim\)1.1-1.5 \(\upmu\)m. In this spectral range, the optical rectification provides the best phase-matching conditions, ideal for studying ultrafast processes in atoms and molecules [6]. The dominant laser source technologies here remain optical parametric amplification (OPA) [7] and optical parametric chirped-pulse amplification (OPCPA) [8]. However, the OPCPA conversion efficiency barely reaches \(\sim\)15%, and the spectral bandwidth is limited by phase matching [9]. An alternative method for frequency conversion may be stimulated Raman scattering (SRS). The particularly wide spectral bandwidth inherent in cascade SRS opens up a promising path for the synthesis of sub-cycle coherent light pulses covering the range from UV to near-IR [10, 11]. The phenomena of stimulated electronic Raman scattering (SERS), stimulated vibrational Raman scattering (SVRS, most often referred to SRS), and stimulated rotational Raman scattering (SRRS) allow for the expansion of the laser spectral range. In this two-photon inelastic scattering process, the energy difference between the incident and scattered photons is attributed to a molecular transition. Cascade SRS leads to the generation of a broadband comb of frequencies separated by the molecular transition energy [12]. Gas SRSconverters, compared to solid-state ones, cover a wider range of wavelengths and have a higher damage threshold as well as operating at a repetition rate of 20 kHz [13]. Raman-active gases such as hydrogen, deuterium, and nitrogen recover even after ionization by high-intensity laser pulses. Moreover, the transmission of Raman-active gases spans from vacuum ultraviolet (VUV) to far infrared (FIR) radiation. Hydrogen has gained popularity due to its largest vibrational shift of 4155 cm\({}^{-1}\) and high Raman gain. However, the rotational shifts of 587 cm\({}^{-1}\) and 342 cm\({}^{-1}\)[14; 15; 16] for ortho- and para-hydrogen are more attractive for generating optical frequency combs and ultrashort pulses [17]. Nevertheless, the vast majority of studies have focused on the excitation of steady-state SVRS, with conversion efficiencies reaching 68% [18] for nanosecond pump pulses. Meanwhile, for picosecond and femtosecond pulses, the efficiency drops significantly [19], since the stimulated Raman gain in the transient regime depends on the integrated energy of the pump pulses and not on the peak power. Moreover, an increase in the instantaneous field intensity leads to unfavorable nonlinear effects such as self-phase modulation (SPM), multiphoton ionization, and harmonic generation, which disrupt SRS [20]. On the other hand, despite the observation of SRRS with nanosecond pump pulses back in 1966 [21], methods for achieving its maximum energy and efficiency in the transient regime have not yet been exhaustively studied. A discrete SRRS spectrum at hydrogen pressures up to 120 atm was observed using 30 ps pump pulses at 1064 nm [22]. Meanwhile, more than 40 mainly anti-Stokes SRRS lines ranging from 239 to 993 nm were obtained [23] at 10 atm using a high-energy 800 fs Ti:sapphire laser. However, most studies lack information on the efficiency and energy of transient SRRS.